Q. No.A \(4.5~\text{cm}\) needle is placed \(12~\text{cm}\) away from a convex mirror of focal length \(15~\text{cm}.\) What is the magnification?
1. \(0.5\)
2. \(0.56\)
3. \(0.45\)
4. \(0.15\)
1. \(0.5\)
2. \(0.56\)
3. \(0.45\)
4. \(0.15\)
Light of wavelength \(5000~\mathring{A}\) falls on a plane reflecting surface. For what angle of incidence is the reflected ray normal to the incident ray?
1. \(37^{\circ}\)
2. \(45^{\circ}\)
3. \(90^{\circ}\)
4. \(0^{\circ}\)
A concave mirror of focal length \(f\) produces an image \(n\) times the size of the object. If the image is real, then the distance of the object from the mirror is:
1. \((n-1)f\)
2. \(\frac{(n-1)}{n}f\)
3. \(\frac{(n+1)}{n}f\)
4. \((n+1)f\)
A man with hypermetropia cannot see objects closer than a distance of \(40~\text{cm}\) from the eye. The power of the lens required so that he can see objects at \(25~\text{cm}\) from the eye is:
1. \(+4.5~\text{D}\)
2. \(+4.0~\text{D}\)
3. \(+1.5~\text{D}\)
4. \(+3.0~\text{D}\)
| 1. | \(30^{\circ}\) | 2. | \(45^{\circ}\) |
| 3. | \(60^{\circ}\) | 4. | \(90^{\circ}\) |
| 1. | \(10~\text{cm}\) | 2. | \(15~\text{cm}\) |
| 3. | \(20~\text{cm}\) | 4. | \(30~\text{cm}\) |
| 1. | \(\dfrac{\pi}{4}\) | 2. | \(\sin^{- 1} \left(\frac{3}{4}\right)\) |
| 3. | \(\frac{1}{2} \sin^{- 1} \left(\frac{3}{4}\right)\) | 4. | \(2\sin^{- 1} \left(\frac{3}{4}\right)\) |
In an astronomical telescope, the focal length of the objective lens is \(100\) cm and of the eyepiece is \(2\) cm. The magnifying power of the telescope for the normal eye is:
| 1. | \(50\) | 2. | \(10\) |
| 3. | \(100\) | 4. | \(\dfrac{1}{50}\) |
The magnifying power of a telescope is \(9\). When it is adjusted for parallel rays the distance between the objective and eyepiece is \(20\) cm. The focal lengths of lenses are:
| 1. | \(10~\text{cm}, 10~\text{cm}\) | 2. | \(15~\text{cm}, 5~\text{cm}\) |
| 3. | \(18~\text{cm}, 2~\text{cm}\) | 4. | \(11~\text{cm}, 9~\text{cm}\) |
A concave mirror of the focal length \(f_1\) is placed at a distance of \(d\) from a convex lens of focal length \(f_2\). A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance \(d\) must be equal to:
1. \(f_1 +f_2\)
2. \(-f_1 +f_2\)
3. \(2f_1 +f_2\)
4. \(-2f_1 +f_2\)
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