The refractive index of the material of the prism for violet colour is 1.69 and that for red is 1.65. If the refractive index for mean colour is 1.66, the dispersive power of the material of the prism

1.  0.66

2.  0.06

3.  0.65

4.  0.69

 

Absolute refractive indices of glass and water are 3/2 and 4/3. The ratio of velocity of light in glass and water will be

1.  4:3

2.  8:7

3.  8:9

4.  3:4

A thin equiconvex lens of power P is cut into three parts A, B, and C as shown in the figure. If ${\mathrm{P}}_1, {\mathrm{P}}_2, \mathrm{and} {\mathrm{P}}_3$ are powers of the three parts respectively, then

1.  ${\mathrm{P}}_1 = {\mathrm{P}}_2 = {\mathrm{P}}_3$

2.  ${\mathrm{P}}_1 > {\mathrm{P}}_2 = {\mathrm{P}}_3$

3.  ${\mathrm{P}}_1 < {\mathrm{P}}_2 = {\mathrm{P}}_3$

4.  ${\mathrm{P}}_2 = {\mathrm{P}}_3 = 2{\mathrm{P}}_1$

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 B'A' as shown in the figure. Maximum magnifying power in this case is :

1.  10

2.  20

3.  5

4.  25

Two identical equiconvex thin lenses each of focal lengths 20 cm, made of material of refractive index 1.5 are placed coaxially in contact as shown. Now, the space between them is filled with a liquid with a refractive index of 1.5. The equivalent power of this arrangement will be:

The length of an astronomical telescope adjusted for parallel light is 90 cm. If the magnifying power of the telescope is 17, then the focal length of eyepiece and objective are respectively:

In the situation shown, the incident monochromatic ray retraces its path after its incidence on the silvered surface. The speed of light inside the prism will be

1.  $3 \mathrm{x} {10}^8 {\mathrm{ms}}^{-1}$

2.  $2 \mathrm{x} {10}^8 {\mathrm{ms}}^{-1}$

3.  $1.41 \mathrm{x} {10}^8 {\mathrm{ms}}^{-1}$

4.  $1.73 \mathrm{x} {10}^8 {\mathrm{ms}}^{-1}$

The sun (diameter D) subtends an angle $\mathrm{\theta }$ radian at the pole of a concave mirror of focal length f. The diameter of the image of the sun formed by the mirror is:

1.  $\mathrm{f\theta }$

2.  $2\mathrm{f\theta }$

3.  $\frac{2\mathrm{f\theta }}{\mathrm{D}}$

4.  $\mathrm{D\theta }$

When a ray is refracted from one medium to another, the wavelength changes from 6000$\stackrel{0}{\mathrm{A}}$ to 4000$\stackrel{0}{\mathrm{A}}$. The critical  angle for the interface will be:

1.  ${\cos }^{-1} \left(\frac{2}{3}\right)$

2.  ${\sin }^{-1}\left(\frac{2}{\sqrt{3}}\right)$

3.  ${\sin }^{-1}\left(\frac{2}{3}\right)$

4.  ${\cos }^{-1}\left(\frac{2}{\sqrt{3}}\right)$

The critical angle for prism is 36$°$. The maximum angle of prism for which the emergent ray is possible is:

1.  $18°$

2.  $36°$

3.  $72°$

4.  $144°$