Arihant - Class X - Light : Reflection and Refraction [ Chapter - 10 ]Contact Number: 8527521718Arihant - Class X - Light : Reflection and Refraction [ Chapter - 10 ]Contact Number: 8527521718Where is the image formed when an object is at large distance from a concave mirror?
Arrange air, glass and water in terms of descending order of refractive index.
How many images are formed for a point source kept in between two plane mirrors M1 and M2 at right angles to each other?
Due to which property of light, sharp shadows of opaque objects are obtained?
Which metal is the best reflector of light?
Is it possible that the laws of reflection change, if we use spherical mirror instead of a plane mirror?
Out of convex mirror and concave mirror, whose focus is situated behind the mirror?
A ray is incident on a plane mirror as shown in figure.
What is the angle of reflection for the above incident ray?
Show the formation of image of the given figure.
The refractive index of diamond is 2.42 and that of glass is 1.52. How much faster does light travel in glass than in diamond?
If the magnification of a body of size 1 m is 2. What is the size of the image?
A ray of light is refracted as shown in figure. Which medium A or B is optically denser than the other?
Between which two points of a concave mirror should an object be placed to obtain a magnification of — 3?
What is the radius of curvature of the spherical mirror in the figure given, if PA = 10 cm?
A point object is placed on the axis of a layered lens, made of two types of transparent materials as shown by different shades. How many images will be formed?
Is it possible that a convergent lens in one medium becomes divergent, when placed in another medium?
What is the minimum distance between an object and its real image formed by a convex lens?
In which of the following cases, magnification is positive?
Can we change focal length of a given spherical mirror by changing the object distance from the mirror?
List out the factors on which refractive index of a medium depends.
Under what conditions there won't be any refraction of light, when it enters from one medium to another?
A ray of light travelling in air is incident on a rectangular glass slab. What will happen?
State two factors which determine lateral displacement of a ray of light passing through a rectangular glass slab
A student is standing in the centre of a room. He wants to fix a plane mirror in front of him on a wall. What should be the smallest length of the mirror taken by him, so as to enable him to see full image of the back wall?
Observe the following incomplete ray diagram of an object where the image A' B' is formed after refraction from a convex lens.
On the basis of above information fill in the blanks.
(i) The position of object AB would have been..........
(ii) Size of the object would have been ......... than the size of image.
Two lenses of power -2.5 D and +1.5 D are placed in contact. Find the total power of the combination of lens. Calculate the focal length of this combination.
"The magnification produced by a spherical mirror is -3." List four informations you obtain from this statement about the mirror/image.
What is meant by power of a lens? What does its sign (+ve or -ve) indicate? State its SI unit. How is this unit related to focal length of a lens?
"A concave mirror of focal length f can form a magnified, erect as well as an inverted image of an object placed in front of it." Justify this statement stating the position of object with respect to the mirror in each case for obtaining these images.
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of object relative to the mirror? Draw a ray diagram to justify your answer.
Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is directed parallel to the principal axis of a convex mirror. Mark on it, the angle of incidence and the angle of reflection.
How can you distinguish between plane mirror, convex mirror and concave mirror by merely looking at the image fanned in each case?
(i) What should be the position of the object when a concave mirror is to be used
(a) as a shaving mirror and
(b) in torches producing parallel beam of light?
(ii) A man standing in front of a minor, finds his image having a very small head and legs of normal size. What type of mirrors are used in
designing such a mirror?
Name the type of mirror used in a solar furnace. How is high temperature achieved by this device?
What should be the position of an object with respect to focus of a convex lens of focal length 20 cm, so that its real and magnified image is obtained? Draw a ray diagram to show the image formation.
An object is placed at 2F1 in front of a convex lens. What is the
(i) position
(ii) size
(iii) nature of image?
Rohit while playing with an old lens discovers that, if he holds the lens 20 cm away from a wall opposite to a window, he can see sharp but inverted images of outside world on the wall. What is the power of the old lens holded by him?
When a plane mirror is placed horizontally on levelled ground at a distance of 40 m from the foot of a tower, the top of the tower and its image in the mirror subtend an angle of 90 at the eye. What is the height of the tower?
If p,q and r denote the object distance, image distance and the radius of curvature respectively, of a spherical mirror, then find out the relation between them.
The absolute refractive indices of glass and water are , respectively. If the speed of light in glass is calculate the speed of light in
(i) vacuum (ii) water
(i) What happens to a ray of light when it travels from one medium to another having equal refractive indices?
(ii) State the cause of refraction of light.
A concave minor is used as a head mirror by ENT specialists. The same mirror can also be used as a shaving minor. Why?
What change do you expect in the focal length of a concave mirror and a convex lens, when immersed in water?
(i) In refraction of light through a rectangular glass slab, the emergent ray is parallel to the direction of the incident ray. Why?
(ii) What happens when a light ray is incident normally on one of the faces of a rectangular glass slab?
(i) An object 1 cm high produces a real image 1.5 cm high when placed at a distance of 15 cm from a concave mirror. Calculate the
position of the image and the magnification.
(ii) Write two uses of concave mirrors.
A concave lens made of a material of refractive index n1 is kept in a medium of refractive index n2. A parallel beam of light is incident on the lens. Trace the path of rays of light parallel to principal axis incident on the concave lens after refraction when
(i) n1 > n1 (ii) n1 = n2
Give reason for each.
(i) " The refractive index of kerosene is 1.44." What is meant by this statement?
(ii) A ray of light strikes a glass slab at an angle of incidence equal to 30. Find the refractive index of glass such that the angle of
refraction is 19.5.
Rohit wants to have an erect image of an object using a converging mirror of focal length 40 cm.
(i) Specify the range of distance where the object can be placed in front of the mirror. Give reason for your answer.
(ii) Will the image be bigger or smaller than the object?
(iii) Draw a ray diagram to show the image formation in this case.
If the image formed by a mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a ray diagram to justify your answer. Where and why do we generally use this type of mirror?
Draw a labelled diagram showing how an image of a small size can be projected on large screen. State two characteristics of an image.
A student wants to project the image of a candle flame on a screen 48 cm in front of a mirror by keeping the flame at a distance of 12 cm from its pole.
(i) Suggest the type of mirror he should use.
(ii) Find the linear magnification of the image produced.
(iii) How far is the image from its object?
(iv) Draw a ray diagram to show the image formation in this case.
Figure shows a ray of light meeting the glass of the window of a car at an angle of incidence of 40.
(i) Assuming that the refractive index of glass is 1.5, find the angle of refraction for this ray in the glass.
(ii) Complete the diagram by sketching the path of the ray through the glass and out on the other side.
(iii) Use the diagram to explain the effect of the glass on what is seen by the driver.
At what distance should an object be placed from a convex lens of focal length 18 cm to obtain an image at 36 cm from it? What will be the magnification produced in this case?
A spherical mirror produces an image of magnification -1 on a screen placed at a distance of 50 cm from the mirror.
(i) Write the type of mirror.
(ii) Find the distance of the image from the object.
(iii) What is the focal length of the mirror?
(iv) Draw the ray diagram to show the image formation in this case.
An object of height 5 cm is placed perpendicular to the principal axis of a concave lens of focal length 10 cm. If the distance of the object from the optical centre of the lens is 20 cm, determine the position, nature and size of the image formed using the lens formula.
(i) Draw a ray diagram to show the refraction of light through a glass slab and mark an angle of refraction and the lateral shift suffered
by the ray of light while passing the slab.
(ii) If the refractive index of glass for light going from air to glass is 3/2, find the refractive index of air for light going from glass to air.
The image of an object formed by a lens is of magnification —1 . If the distance between the object and its image is 60 cm, what is the focal length of the lens? If the object is moved 20 cm towards the lens, where would the image be formed? State reason and also draw a ray diagram in support of your answer.
When an object is placed at a distance of 60 cm from a convex spherical mirror, the magnification produced is . Where should the object be placed to get a magnification of ?
Find the distance at which an object should be placed in front of a convex lens of focal length 10 cm to obtain an image of double its size.
A 6 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 25 cm. The distance of the object from the lens is 40 cm.
By calculation determine
(i) the position and
(ii) the size of the image formed.
A student focussed the image of a candle flame on a white screen by placing the flame at various distances from a convex lens. He noted his observation in the following table.
S.No. | Distance of the Screen from Lens (cm) | Distance of the Flame from Lens (cm) |
I | 20 | 60 |
II | 24 | 40 |
III | 30 | 30 |
IV | 40 | 24 |
V | 70 | 12 |
Analyse the above table and give the answers of the following questions.
(i) What is the focal length of convex lens?
(ii) Which set of observation is incorrect and why?
(iii) Draw the ray diagram to show the image formation for any correct set of observation.
Ravi is given lenses with powers +5D, -5D, +10D, -10D and -20D. Considering a pair of lenses at a time, which two lenses will he select to have a combination of total focal length when two lenses are kept in contact in each case.
(i) -10 cm
(ii) 20 cm
(iii) - 20 cm
A convex lens made of a material of refractive index n2 is kept in a medium of refractive index n1. A parallel beam of light is incident on the lens. Draw the path of rays of light emerging from the convex lens, if
(i) n1 < n2 (ii) n1 = n2 (iii) n1 > n2
If an object is held at a distance of 60 cm from a convex mirror of focal length 20 cm. At what distance from the convex mirror, should a plane mirror be held, so that images in the two mirrors coincide?
It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm.
(i) What should be the range of distance of an object placed in front of the mirror?
(ii) Will the image be smaller or larger than the object? Draw ray diagram to show the formation of image in this case.
(iii) Where will the image of this object be, if it is placed 24 cm in front of the mirror? Draw ray diagram for this situation also to justify
your answer.
Show the positions of pole, principal focus and the centre of curvature in the above ray diagrams.
A student wants to project the image of a candle flame on the walls of school laboratory by using a lens.
(i) Which type of lens should he use and why?
(ii) At what distance in terms of focal length F of the lens should he place the candle flame, so as to get
(a) a magnified and
(b) a diminished image respectively on the wall?
(iii) Draw ray diagrams to show the formation of the image in each case.
(i) Two lenses have power of
(a) +2 D (b) -4 D.
What is the nature and focal length of each lens?
(ii) An object is kept at a distance of 100 cm from each of above lenses. Calculate.
(a) image distance and
(b) magnification in each of the two cases.
One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer.
A 4 cm tall object is placed perpendicular to principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 15 cm. Find the nature, position and the size of the image.
A student wants to project the image of a candle flame on the walls of the school laboratory by using a mirror.
(i) Which type of mirror should he use and why?
(ii) At what distance, in terms of focal length f of the mirror, should he place the candle flame to get the magnified image on the wall?
(iii) Draw a ray diagram to show the formation of the image in this case.
(iv) Can he use this mirror to project a diminished image of the candle flame on the same wall? State 'how., if your answer is 'yes' and
'why not', if your answer is 'no'
(i) Draw a ray diagram to show the formation of image by a convex lens when an object is placed in front of the lens between its optical
centre and principal focus.
(ii) In the above ray diagram mark the object distance (u) and the image distance (v) with their proper signs (+ ve or - ve as per the
new cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.
(iii) Find the power of convex lens which forms a real and inverted image of magnification -1 of an object placed at a distance of 20 cm
from its optical centre.
(i) Define optical centre of spherical lens.
(ii) A divergent lens has a focal length of 20 cm. At what distance should an object of height 4 cm from the optical centre of the lens be
placed, so that its image is formed 10 cm away from the lens. Find the size of the image also.
(iii) Draw a ray diagram to show the formation of image in above situation.
(i) Define the following terms in the context of spherical mirrors.
(a) Pole (b) Centre of curvature
(c) Principal axis (d) Principal focus
(ii) Draw ray diagrams to show the principal focus of a
(a) concave mirror
(b) convex mirror.
(iii) Consider the following diagram in which M is a mirror and P is an object and Q is its magnified image formed by the mirror.
State the type of mirror M and one characteristic property of the image Q.
(i) Define the focal length of a spherical lens.
(ii) A divergent lens has a focal length of 30 cm. At what distance should an object of height 5 cm from the optical center of the lens be
placed, so that its image is formed 15 cm away from the lens? Find the size of the image also.
(iii) Draw a ray diagram to show the formation of the image in the above situation.
What is meant by power of a lens? Define its unit.
You have two lenses A and B of focal lengths +10 cm and -10 cm, respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer.
A student has three concave mirrors A, B and C of focal lengths 20 cm,15 cm and 10 cm, respectively. For each concave mirror, he performs the experiment of image formation for three values of object distance of 30 cm, 10 cm and 20 cm.
Give reasons for the following:
(i) For the three object distances, identify the mirror which will form an image equal in size to that of object. Find at least one value
of object distance.
(ii) Out of the three mirrors, identify the mirror which would be preferred to be used for shaving purpose.
(iii) For the mirror B, draw ray diagram for image formation for any two given values of object distance.
An air bubble in water is shown in the figure. Three rays of light are incident on the air bubble.
The angle of incidence of ray 1 on the air bubble is greater than the critical angle. The angle of incidence of ray 2 on the air bubble is less than the critical angle. Ray 3 is perpendicular to the surface of the bubble.
(i) In figure at the point where ray 1 meets the air bubble, mark
(a) the normal to the surface
(b) the angle of incidence
(ii) Complete the ray diagram to show how all three rays continue after they meet the air bubble.
(iii) Define refractive index of water. If the speed of light in air is 3 x 108 ms-1 and the speed of light in water is 2.2 x 108 ms-1. Calculate
the refractive index of water.
(1) Explain the following terms related to spherical lenses.
(i) Centres of curvature (ii) Principal axis
(iii) Optical centre (iv) Principal focus
(2) At what distance from a concave lens of focal length 20 cm, should a 6 cm tall object be placed so that it forms an image at 15 cm
from the lens? Also, determine the size of the image formed.
A thin converging lens form a real magnified image and virtual magnified image of an object in front of it.
(i) Write the positions of the objects in each case.
(ii) Draw ray diagrams to show the image formation in each part.
(iii) How will the following be affected on cutting this lens into two halves along the principal axis?
(a) Focal length
(b) Intensity of the image formed by halt lens.
You are provided with two convex lenses of same aperture and different thickness. Which one of them will be of shorter focal length?
What is the nature of an image formed by a thin convex lens for a distant object? What change do you expect, if the lenses were rather thick?
Sometimes, the image formed by a convex lens of an object placed at 2F1 is not of the same size and at location 2F2 on the other side of the convex lens. What could be the possible reason(s) for such a situation?
A student performs an experiment on finding the focal length of a convex lens by keeping a lighted candle on one end of a laboratory table, a screen on its other end and the lens between them as shown in the figure.
The positions of the three are adjusted to get a sharp image of the candle flame on the screen. If now the candle flame were to be replaced by a distant lamp on a faraway electric pole, how would the student be able to get a sharp image of this distant lamp on the screen? Explain.
A student traces the path of a ray of light passing through a rectangular glass slab for three different values of angle of incidence namely 30, 45 and 60. He produces the incidence ray and measures the perpendicular distance d between the produced incident and emergent ray. What will he observe? Explain.
A student has to perform the experiment on finding the image distance for varying object distances in case of a convex lens. Which apparatus does he need?
While tracing the path of ray of light through a glass slab, the angle of incidence is generally taken between 30 and 60. Explain, the reason on the basis of your performing this experiment of different angles of incidence.
In an experiment with a rectangular glass slab, a student observed that a ray of light incident at an angle of 60 with the normal on one face of the slab, after refraction strikes the opposite face of the slab before emerging out into air making an angle of 42 with normal. Draw a labelled diagram to show the path of this ray. What value would you assign to the angle of refraction and angle of emergence?
A student focuses the image of a well illuminated distant object on a screen using a convex lens. After that he gradually moves the object towards the lens and each times focuses its image on the screen by adjusting the lens.
(i) In which direction towards the screen or away from the screen, does he move the lens?
(ii) What happens to the size of the image does it decrease or increase?
(iii) What happens to the image on the screen when he moves the object very close to the lens?
On the way from Kanpur to Delhi there were four friends. Sunil was driving the car and saw from his side mirror that the car which was behind their car had met an accident. He suddenly applied the brake even after his friends asked him to leave the situation as it is. But Sunil did not agree and got down of car and persuaded his friends to help the injured. All of them took the injured person to the nearest hospital.
After taking first aid from hospital the victim thanked and pleased them for saving his life.
Read the above passage and answer the following questions:
(i) Name the type of mirror from which Sunil saw the accident.
(ii) Why this mirror is used as a side mirror in vehicles?
(iii) What can you learn from the Sunil's character?
Two friends Kapil and Rohit were studying in the same class. One day Rohit observed that Kapil was having pain in gums during lunch time. Rohit told Kapil that his father was dentist and asked him to visit his father's clinic. Rohit's father examined Kapil with the help of a mirror and advised him not to eat too many chocolates and son drinks.
Kapil followed the advice of the doctor and soon he got recovered.
After that he starts taking care of his mouth, as he washes his mouth properly after every meal and also starts taking a calcium rich diet.
Read the given passage and answer the following questions:
(i) Identify the mirror used by the dentist.
(ii) Name the phenomenon of light by which doctor is able to examine Kapil.
(iii) What values are shown by doctor, his son and Kapil?
Rhea and Harnoor were at the dining table having their dinner. An argument broke out between them about convex and concave mirror as to which mirror forms an inverted image. Losing no time Rhea took a highly polished spoon. She made Harnoor look into the depressed surface of the spoon and then the bulging surface.
The images formed in the two cases were different. In the first case, the image formed was inverted while in the second case, it was erect. Then, she explained to Harnoor about the two surfaces acting as mirrors and also which formed an inverted image. This at once stopped the argument.
(i) Which of the two mirrors forms an inverted image : concave or convex?
(ii) What are the values shown by Rhea and Harnoor?
(iii) Give one use of a concave mirror.
At one of the blind ends of a road in a colony lot of accidents used to take place. One day Kunwar moved into a house near the blind end.
On a certain day he saw an accident take place at the blind end. He at once rushed to the spot and helped the victims with first aid. He, then telephoned for an ambulance. Later on he met the President of the welfare committee of the colony and requested him to install huge convex mirrors at both ends of the blind end. After the installation of the mirrors the accident rates suddenly dropped.
(i) What according to you are the values displayed by Kunwar?
(ii) Why did Kunwar advise the installation of convex mirror?