In the diagram shown below, the image of the point object \(O\) is formed at \(l\) by the convex lens of focal length \(20\) cm, where \(F_1\) and \(F_2\) are foci of the lens. The value of \(x'\) is:
1. | \(10\) cm | 2. | \(20\) cm |
3. | \(30\) cm | 4. | \(40\) cm |
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. |
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. | \(25\) |
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 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
Choose the correct mirror image of the figure:
1. | ![]() |
2. | ![]() |
3. | ![]() |
4. | ![]() |
In the following diagram, what is the distance \(x\) if the radius of curvature is \(R= 15\) cm?
1. | \(30\) cm | 2. | \(20\) cm |
3. | \(15\) cm | 4. | \(10\) cm |
The distance between the object and its real image formed by a concave mirror is minimum when the distance of the object from the centre of curvature of the mirror is: [\(f\rightarrow\) focal length of the mirror]
1. | Zero | 2. | \(\dfrac{f}{2}\) |
3. | \(f\) | 4. | \(2f\) |
A lens forms an image of a point object placed at distance \(20\) cm from it. The image is formed just in front of the object at a distance \(4\) cm from the object (and towards the lens). The power of the lens is:
1. \(-2.25\) D
2. \(1.75\) D
3. \(-1.25\) D
4. \(1.4\) D