Laws of Refraction Using Huygens' Principle

Q. The phase change in reflected wave, when light wave suffers reflection at the interface from air to glass is

1. 0
2. $\frac{\pi }{2}$
3. $\pi$
4. $2\pi$

Q. A transverse wave travelling in a denser medium is reflected from a rarer medium. Then,

1. an incident crest is reflected as a crest
2. an incident crest is reflected as a trough
3. there is a phase change of $2\pi$ rad
4. there is a phase change of $\pi /2$ rad

Q. Which of the following statement is incorrect about the Raman effect?

1. Raman effect can be seen by passing a monochromatic beam of light through benzene
2. During scattering, the wavelength of the light used may change
3. In Raman scattering the wavelength of the scattered light is the same as that of the incident light
4. The wavelength of the monochromatic light used to show the Raman effect is approximately $4358$ $\stackrel{o}{A}$

Q. Which of the following statements indicates that light waves are transverse

1. Light waves can travel in vacuum
2. Light waves show interference
3. Light waves can be polarized
4. Light waves can be diffracted

Q. To ensure almost 100 per cent transmittivity, photographic lenses are often coated with a thin layer of dielectric material. The refractive index of this material is intermediated between that of air and glass (which makes the optical element of the lens). A typically used dielectric film is $Mg{F}_2$ (n = 1.38). What should the thickness of the film be so that at the center of the visible spectrum ($5500\stackrel{o}{A}$) there is maximum transmission.

1. $5000\stackrel{o}{A}$
2. $2000\stackrel{o}{A}$
3. $1000\stackrel{o}{A}$
4. $3000\stackrel{o}{A}$

Q. On the basis of Huygen's Wave theory of light, show that angle of reflection is equal to angle of incidence. You must draw a labelled diagram for this derivation.

Q. In figure, PQ represents a plane wavefront and AO and BP the corresponding extreme rays of monochromatic light of wavelength '$\lambda$'. The value of angle $\theta$ for which the ray BP and the reflected ray OP interfere constructively is given by:

1. cos$\theta =\frac{3\lambda }{4d}$
2. cos$\theta =\frac{\lambda }{4d}$
3. sec$\theta =\frac{\lambda }{3d}$
4. sec $\theta =\frac{2\lambda }{3d}$

Q. When light suffers reflection at the interface between water and glass, the change of phase in the reflected wave is

1. Zero
2. $\pi$
3. $\pi$/2
4. 2$\pi$

Q. In the figure, $PQ$ represents a plane wave front and $AO$ and $BP$ the corresponding extreme rays of monochromatic light of wavelength $\lambda$. The value of angle $\theta$ for which the ray $BP$ and the reflected ray $OP$ interfere constructively is given by

1. $cos\theta =\frac{\lambda }{2d}$
2. $cos\theta =\frac{\lambda }{4d}$
3. $sec\theta =\frac{\lambda }{3d}$
4. $sec\theta =\frac{2\lambda }{3d}$

Q. For what distance ray optics a good approximation when the aperture is 4 mm wide and the wavelength is 500nm?

1. $69m$
2. $16m$
3. $8m$
4. $32m$