A concave lens is made of three layers of glass of three different materials as shown in the furure. A point object is placed on its axis. Number of images of the object is -

1. 2

2. 3

3. 4

4. 1

An object is placed at a distance of 20 cm from the thin lens as shown in the figure. The points $C_1$ and $C_2$ denote centres of curvature. The magnification produced by the lens is (Refractive index of glass is 1.5)

1.  -2

2.  +2

3.  -1/2

4.  +1/2

A lens forms image of a point object placed at distance 20 cm from it, just in front of the object at distance 4 cm from the object towards the lens. The power of lens is

(1) -2.25 D

(2) 1.75 D

(3) -1.25 D

(4) 1.4 D

A point object O is placed on the principal axis of the convex lens of focal length f = 20 cm at a distance of 40 cm. The diameter of the lens is 10 cm. An eye is placed 60 cm to the right of lens and a distance h below the principal axis. The maximum value of h to see the image is-

1. Zero 

2. 2.5cm

3. 5cm

4.10cm 

If the wavelength of a ray of light from a source of lights is 3000 $\stackrel{0}{A}$in air, then the wavelength of that ray of light in a liquid in which S is placed will be:

(1) 4000 $\stackrel{0}{A}$

(2) 1500 $\stackrel{0}{A}$

(3) 9000 $\stackrel{0}{A}$

(4) 3500 $\stackrel{0}{A}$

A ray of light incident at an angle i is refracted at angle r into a glass slab of thickness t. The lateral displacement of the emergent ray is

1.  $\frac{t \sin i}{\cos r}$

2.  $\frac{t \sin \left(i-r\right)}{\cos r}$

3.  t sin (i-r) cos r

4.  $\frac{t \sin \left(i+r\right)}{\cos r}$

Chromatic aberration is absent in

(1) Plano-convex lens

(2) Plano concave lens

(3) Concave mirror

(4) Bifocal lens

For a convex lens of focal length 15 cm the dispersive power of its material is 0.05. The longitudinal chromatic aberration of the lens is

(1) 3.6$\times {10}^{-4} m$

(2) 700 cm

(3) 7.5 mm

(4) 1.34 $\mu m$

A convex mirror of a focal length f (in air) is immersed in water $\left(\mu =\frac{4}{3}\right)$. Focal length of the mirror in water will be

1.  f

2.  $\frac{4}{3}f$

3.  $\frac{3}{4}f$

4.  4f

1. \(25~\text{m/s}\)
2. \(25\sqrt{2}~\text{m/s}\)
3. \(50~\text{m/s}\)
4. \(50\sqrt{2}~\text{m/s}\)