A given ray of light suffers minimum deviation in an equilateral prism P. Additional prisms Q and R of identical

shape and material are now added to P, as shown in the figure. The ray will suffer

• same deviation

• greater deviation

• total internal reflection

• no deviation

The aperture of the objective lens of a telescope is made large so as to

• increase the resolving power of the telescope

• increase the magnifying power of the telescope

• to focus on distant objects

• make image aberrationless

A lamp hanging 4 metres above the table is lowered by 1 metre. The illumination on the table

• decreased by 25%

• increased by 25%

• decreased by 66.7%

• increased by 77.7%

In Young's double slit experiment, the fringe width is β, if the entire arrangement is placed in a liquid of refractive index n, the fringe width becomes

• nβ

• $\frac{\mathrm{\beta }}{\mathrm{n} + 1}$

• $\frac{\mathrm{\beta }}{\mathrm{n} - 1}$

• $\frac{\mathrm{\beta }}{\mathrm{n}}$

Yellow light is used in single slit diffraction experiment with slit width 0.6 mm. If yellow light is replaced by X-rays, then the pattern will reveal that

• no diffraction pattern

• that the central maxima narrower

• less number of fringes

• more number of fringes

In an interference experiment, third bright fringe is obtained at a point on the screen with a light of 700 nm. What should be the wavelength of the light source in order to obtain 5th bright fringe at the same point ?

• 630 nm

• 500 nm

• 420 nm

• 750 nm

If a ray of light in a denser medium enters into a rarer medium at an angle of incidence i, the angle of reflection and refraction are respectively r and r'. If the reflected and refracted rays are at right angles to each other, the critical angle for the given pair of media is

• sin^-1 (tan r')

• sin^-1 (tan r)

• tan^-1 (sin i)

• cot (tan i)

The phenomenon of rotation of plane polarised light is called

• Kerr effect

• double refraction

• optical activity

• dichroism

49.

As a result of interference of two coherent sources of light energy is

• redistributed and the distribution does not vary with time

• increased

• redistributed and that distribution changes with time

• decreased

There are n₁ photons of frequency v₁ in a beam oflight. In an equally energetic beam there are n₂ photons of frequency v₂. Then the correct relation

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{\mathrm{v}}_1}{{\mathrm{v}}_2}$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = 1$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{\mathrm{v}}_2}{{\mathrm{v}}_1}$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{{\mathrm{v}}_2}^2}{{{\mathrm{v}}_1}^2}$