The distance between the object and its real image formed by a concave mirror is minimum when the distance of the object from the center of curvature of the mirror is: (where\(f\) is the focal length of the mirror)
1. zero
2. \(\dfrac{f}{2}\)
3. \(f\)
4. \(2f\)
In the following diagram, what is the distance \(x\) if the radius of curvature is \(R= 15\text{cm}?\)
1. | \(30\text{cm}\) | 2. | \(20\text{cm}\) |
3. | \(15\text{cm}\) | 4. | \(10\text{cm}\) |
In the diagram shown below, the image of the point object \(O\) is formed at \(l\) by the convex lens of focal length \(20~\text{cm},\) where \(F_1\) and \(F_2\) are foci of the lens. The value of \(x'\) is:
1. | \(10~\text{cm}\) | 2. | \(20~\text{cm}\) |
3. | \(30~\text{cm}\) | 4. | \(40~\text{cm}\) |
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. |
The focal lengths of the objective and eyepiece of a compound microscope are \(2\text{cm}\) and \(6.25\text{cm}\) respectively. An object \(AB\) is placed at a distance of \(2.5\text{cm}\) from the objective which forms the image \(A'B'\) as shown in the figure. The maximum magnifying power in this case, will be:
1. | \(10\) | 2. | \(20\) |
3. | \(5\) | 4. | \(25\) |
A concave lens of focal length \(25~\text{cm}\) produces an image \(\frac{1}{10}\text{th}\) of the size of the object. The distance of the object from the lens is:
1. | \(225~\text{cm}\) | 2. | \(250~\text{cm}\) |
3. | \(150~\text{cm}\) | 4. | \(175~\text{cm}\) |
A mark on the surface of the 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 the sphere is:
1. \(15~\text{cm}\)
2. \(5~\text{cm}\)
3. \(7.5~\text{cm}\)
4. \(2.5~\text{cm}\)
The correct mirror image of the figure is:
1. | ![]() |
2. | ![]() |
3. | ![]() |
4. | ![]() |
A lens forms an image of a point object placed at distance \(20~\text{cm}\) from it. The image is formed just in front of the object at a distance \(4~\text{cm}\) from the object (and towards the lens). The power of the lens is:
1. \(-2.25~\text D\)
2. \(1.75~\text D\)
3. \(-1.25~\text D\)
4. \(1.4~\text D\)