A concave lens of focal length \(25\) cm produces an image \(\frac{1}{10}\text{th}\) the size of the object. The distance of the object from the lens is:
1. | \(225\) cm | 2. | \(250\) cm |
3. | \(150\) cm | 4. | \(175\) cm |
A convex mirror of focal length \(f\) forms an image which is \(\frac{1}{n}\) times the length of the object. The distance of the object from the mirror is:
1. \((n-1)f\)
2. \(\left( \frac{n-1}{n} \right)f\)
3. \(\left( \frac{n+1}{n} \right)f\)
4. \((n+1)f\)
A mark on the surface of sphere \(\left(\mu= \frac{3}{2}\right)\) is viewed from a diametrically opposite position. It appears to be at a distance \(15~\text{cm}\) from its actual position. The radius of sphere is:
1. \(15\) cm
2. \(5\) cm
3. \(7.5\) cm
4. \(2.5\) cm
A light ray from the air is incident (as shown in the figure) at one end of glass fibre (refractive index \(\mu= 1.5\)) making an incidence angle of \(60^{\circ}\) on the lateral surface so that it undergoes a total internal reflection. How much time would it take to traverse the straight fibre of a length of \(1\) km?
1. \(3.33~\mu\text{s}\)
2. \(6.67~\mu\text{s}\)
3. \(5.77~\mu\text{s}\)
4. \(3.85~\mu\text{s}\)
Choose the correct mirror image of the figure:
1. | ![]() |
2. | ![]() |
3. | ![]() |
4. | ![]() |
If there had been one eye of a man, then:
1. | image of the object would have been inverted |
2. | visible region would have decreased |
3. | image would have not been seen in three dimensional |
4. | Both (2) and (3) |
The near point of a person is 50 cm and the far point is 1.5 m. The spectacles required for reading purposes and for seeing distant objects are respectively:
1. + 2D, \(-\frac{2}{3}~D\)
2. \(+\frac{2}{3}~D\), - 2 D
3. - 2 D, \(+\frac{2}{3}~D\)
4. \(-\frac{2}{3}~D\), + 2 D
Focal lengths of objective and eyepiece of a compound microscope are \(2\) cm and \(6.25\) cm respectively. An object \(AB\) is placed at a distance of \(2.5\) cm from the objective which forms the image \(A'B'\) as shown in the figure. Maximum magnifying power in this case, will be:
1. | \(10\) | 2. | \(20\) |
3. | \(5\) | 4. | \(25\) |
If the space between two convex lenses of glass in the combination shown in the figure below is filled with water, then:
1. | the focal length of the system will decrease. |
2. | the focal length of the system will increase. |
3. | the power of the system will increase. |
4. | the power of the system will become infinite. |
An astronomical telescope has angular magnification of \(20\) in its normal adjustment. Focal length of eyepiece is \(4\) cm. Distance between objective and eyepiece is:
1. | \(80\) cm | 2. | \(84\) cm |
3. | \(76\) cm | 4. | \(90\) cm |