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Huygens' wave theory predicted that if a light ray bends towards the normal upon refraction, the speed of light in the second medium would be:
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.
Which of the following optical phenomena cannot be satisfactorily explained by Huygens' wave theory in its original formulation?
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.
When can a ray of light be defined as the path of energy propagation in the context of geometrical optics?
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 energy of a wave travels in what direction relative to the wavefront?
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.
What is the relationship between the speed of light ($v$) in a medium and its refractive index ($n$)?
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.
According to Huygens' principle, after a plane wavefront F1F2 passes through a medium, what is the nature of the wavefront G1G2 at a later time t?
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.
A hollow spherical shell of uniform density has mass M and radius R. A point mass m is placed outside the shell at a distance r from its center. What is the gravitational force exerted by the shell on the point mass?
According to the NCERT text, 'The force of attraction between a hollow spherical shell of uniform density and a point mass situated outside is just as if the entire mass of the shell is concentrated at the centre of the shell.' Therefore, the force is $G \frac{Mm}{r^2}$.
A point mass m is placed inside a hollow spherical shell of uniform density. What is the gravitational force exerted by the shell on the point mass?
As stated in the NCERT text, 'The force of attraction due to a hollow spherical shell of uniform density, on a point mass situated inside it is zero.' This is because the gravitational forces from various regions of the shell cancel each other completely.
Consider a homogeneous solid sphere of mass M and radius R. A particle of mass m is placed inside the sphere at a distance r from its center ($r < R$). In which direction does the gravitational force on the particle act?
The NCERT text states, 'If a particle is inside a homogeneous solid sphere, the force on the particle acts toward the centre of the sphere. This force is exerted by the spherical mass interior to the particle.'
Gravitational shielding is not possible. Which of the following statements best explains this phenomenon?
The NCERT text highlights, 'The gravitational for ce on a particle inside a spherical shell is zer o. However, (unlike a metallic shell which shields electrical forces) the shell does not shield other bodies outside it from exerting gravitational forces on a particle inside. Gravitational shielding is not possible.'
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The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.