NEET Practice Questions (MCQs) with Answers & Solutions

Table 4.2, under 'Segmentation', lists 'Absent' for Platyhelminthes.

Table 4.2, under 'Respiratory System', lists 'Absent' for Platyhelminthes.

The text states, 'The wave model could satisfactorily explain the phenomena of reflection and refraction; however, 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 experiments.

The context explicitly describes 'refraction of a plane wave by (a) a thin prism, (b) a convex lens. (c) Reflection of a plane wave by a concave mirror.' While total internal reflection is mentioned as a consequence of refraction in rarer mediums, its direct explanation using wavefront behavior, like the others, is not provided in detail in these specific excerpts regarding wavefront transformations through prisms, lenses, and mirrors.

The passage states, 'In Fig. 10.7(b) we consider a plane wave incident on a thin convex lens; the central part of the incident plane wave traverses the thickest portion of the lens and is delayed the most. The emerging wavefront has a depression at the centre and therefore the wavefront becomes spherical and converges to the point F which is known as the focus.'

The text explicitly states: 'The above equation implies that when a wave gets refracted into a denser medium ($v_1 > v_2$) the wavelength and the speed of propagation decrease but the frequency $\nu (= v/\lambda)$ remains the same.'

The context explains, 'Thus, if we wish to determine the shape of the wavefront at t = t, we draw spheres of radius $vt$ from each point on the spherical wavefront where v represents the speed of the waves in the medium. If we now draw a common tangent to all these spheres, we obtain the new position of the wavefront at t = t.'

The text states, 'The corpuscular model predicted that if the ray of light (on refraction) bends towards the normal then the speed of light would be greater in the second medium.'

The text mentions, 'Thus, if $i = i_c$ then $\sin r = 1$ and $r = 90^\circ$. Obviously, for $i > i_c$, there cannot be any refracted wave... for all angles of incidence greater than the critical angle, we will not have any refracted wave and the wave will undergo what is known as total internal reflection.'

From the derivations, $\sin i = \frac{v_1 \tau}{AC}$ and $\sin r = \frac{v_2 \tau}{AC}$. Dividing the two equations gives $\frac{\sin i}{\sin r} = \frac{v_1}{v_2}$.