Physics MCQs for NEET — Practice Questions with Answers

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

The text states, 'In Fig. 10.7(c) a plane wave is incident on a concave mirror and on reflection we have a spherical wave converging to the focal point F.'

The text notes, '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 is in contradiction to the prediction made by using the corpuscular model of light. It was much later confirmed by experiments where it was shown that the speed of light in water is less than the speed in air confirming the prediction of the wave model; Foucault carried out this experiment in 1850.'

The text provides Snell's Law as '$n_1 \sin i = n_2 \sin r$ (10.6)'.

The text explains, 'Clearly, since the speed of light waves is less in glass, the lower portion of the incoming wavefront (which travels through the greatest thickness of glass) will get delayed resulting in a tilt in the emerging wavefront...'

The discussion concludes, 'From the above discussion it follows that the total time taken from a point on the object to the corresponding point on the image is the same measured along any ray. For example, when a convex lens focuses light to form a real image, although the ray going through the centre traverses...'

The text states, 'We now consider refraction of a plane wave at a rarer medium, i.e., $v_2 > v_1$. Proceeding in an exactly similar manner we can construct a refracted wavefront as shown in Fig. 10.5. The angle of refraction will now be greater than angle of incidence...'

The context explains, 'In order to construct the reflected wavefront we draw a sphere of radius $vt$ from the point A as shown in Fig. 10.6. Let CE represent the tangent plane drawn from the point C to this sphere. Obviously AE = BC = $vt$'. Therefore, AE and BC are equal.

The NCERT text states: 'The main reason for preferring use of ac voltage over dc voltage is that ac voltages can be easily and efficiently converted from one voltage to the other by means of transformers.'

The NCERT text mentions: 'Joule heating is given by $i^2R$ and depends on $i^2$ (which is always positive whether i is positive or negative) and not on i. Thus, there is Joule heating and dissipation of electrical energy when an ac current passes through a resistor.'