Light of wavelength 5000 Å falls on a plane reflecting surface. For what angle of incidence is the reflected ray normal to the incident ray?
1. 37º
2. 45º
3. 90º
4. 0º

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. $\left\{\frac{(n-1)}{n}\right\}f$

3. $\left\{\frac{(n+1)}{n}\right\}f$

4. $(n+1) f$

A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. What is the magnification?

1. 0.5

2. 0.56

3. 0.45

4. 0.15

A man with hypermetropia cannot see objects closer than a distance of 40 cm from the eye. The power of the lens required so that he can see objects at 25 cm from the eye is:

1. +4.5 D

2. +4.0 D

3. 1.5 D

4. +3.0 D

For a light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is:

1. 30^o

2. 45^o

3. 60^o 

4. 90^o

A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be:

1. 10 cm

2. 15 cm

3. 20 cm

4. 30 cm

A plane mirror is placed horizontally inside water $(\mathrm{\mu }=4/3)$. A ray falls normally on it. Then the mirror is rotated through an angle $\mathrm{\theta }$. The minimum value of $\mathrm{\theta }$ for which the ray does not come out of the water surface is:
                                  

1. $\frac{\mathrm{\pi }}{4}$

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. $\frac{1}{50}$

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 cm, 10 cm

2. 15 cm, 5 cm

3. 18 cm, 2 cm

4. 11 cm, 9 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. $-2f_1+f_2$