Wave Optics MCQs for NEET — Physics Questions with Answers

The NCERT text mentions, 'The wave theory was not readily accepted primarily because of Newton’s authority and also because light could travel through vacuum and it was felt that a wave would always require a medium to propagate from one point to the other.' Option o3 highlights this key reason.

The NCERT states, 'Huygens argued that the amplitude of the secondary wavelets is maximum in the forward direction and zero in the backward direction; by making this adhoc assumption, Huygens could explain the absence of the backwave.' Option o3 matches this perfectly.

The NCERT states, 'If we have a point source emitting waves uniformly in all directions, then the locus of points which have the same amplitude and vibrate in the same phase are spheres and we have what is known as a spherical wave.' Thus, for a point source, a spherical wave is formed.

The NCERT states, 'At a large distance from the source, a small portion of the sphere can be considered as a plane and we have what is known as a plane wave.' Therefore, at large distances, a spherical wavefront approximates a plane wave.

The NCERT states, '...it predicted that on refraction if the wave bends towards the normal then the speed of light would be less in the second medium.' This was later confirmed by Foucault's experiment.

The NCERT mentions, 'Most interference and diffraction effects exist even for longitudinal waves like sound in air. But polarisation phenomena are special to transverse waves like light waves.' Huygens' original theory treated light as longitudinal, and thus could not explain polarization, which requires transverse waves. The text also mentions that 'the phenomenon of polari sation which is based on the fact that the light waves are transverse electromagnetic waves,' which came much later with Maxwell's theory.

The NCERT states, 'Indeed, the branch of optics in which one completely neglects the finiteness of the wavelength is called geometrical optics and a ray is defined as the path of energy propagation in the limit of wavelength tending to zero.' Option o2 directly reflects this.

The NCERT explicitly states, 'The energy of the wave travels in a direction perpendicular to the wavefront.' This is a fundamental concept in wave propagation.

The NCERT provides the equations: $n_1 = c/v_1$ and $n_2 = c/v_2$. This implies that the refractive index is given by $n = c/v$, where $c$ is the speed of light in vacuum. Option o2 is correct.

For a plane wave, Fig 10.3 and its description state, 'F1F2 is the plane wavefront at t = 0 and G1G2 is the wavefront at a later time t. The lines A1A2, B1B2 … etc., are normal to both F1F2 and G1G2 and represent rays.' This signifies that G1G2 is also a plane wavefront, parallel to F1F2, maintaining the perpendicularity of rays. Option o1 is correct.