Optics MCQs for NEET — Physics Questions with Answers

The NCERT text explicitly states regarding this formula: 'It holds for any curved spherical surface.' (Page 233, after presenting Equation 9.16). This formula is foundational for understanding refraction at a single spherical interface before moving on to lens maker's formula which uses two such surfaces.

As described in NCERT Section 10.3.1 (Wave Optics) and depicted in Figure 10.7(b): '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.' This illustrates the application of Huygens' principle to lens behavior.

From the NCERT text, 'The rays are incident from a medium of refractive index $n_1$, to another of refractive index $n_2$.' (Section 9.5.1). Therefore, $n_1$ is the refractive index of the medium of incidence.

The NCERT text (Wave Optics, page 259) states: 'From the above equation, we get the important result that if $r < i$ (i.e., if the ray bends toward the normal), the speed of the light wave in the second medium ($v_2$) will be less then the speed of the light wave in the first medium ($v_1$).' This is a direct consequence of Snell's law $n_1 \sin i = n_2 \sin r$ and $n = c/v$, which implies $ \frac{\sin i}{\sin r} = \frac{n_2}{n_1} = \frac{v_1}{v_2} $. If $v_2 < v_1$, then $ \frac{v_1}{v_2} > 1 $, so $ \frac{\sin i}{\sin r} > 1 $, which means $\sin i > \sin r$, and thus $i > r$ (for acute angles).

The introductory paragraph of Chapter 9 (Ray Optics and Optical Instruments) states: 'In this chapter, we consider the phenomena of reflection, refraction and dispersion of light, using the ray picture of light. Using the basic laws of reflection and refraction, we shall study the image formation by plane and spherical reflecting and refracting surfaces.' This clearly defines the scope and approach of ray optics.

The NCERT text explicitly states: 'We have, for small angles, $\tan \angle NOM = \frac{MN}{OM}$'. This is a direct application of the small angle approximation where $\tan \theta \approx \theta \approx \sin \theta$ and relating it to the sides of the right-angled triangle formed by the perpendicular from N to the principal axis.

According to the NCERT text, 'A simple microscope has a limited maximum magnification (≤ 9) for realistic focal lengths.'

The NCERT states: 'The lens nearest the object, called the objective, forms a real, inverted, magnified image of the object.'

The NCERT states: 'This serves as the object for the second lens, the eyepiece, which functions essentially like a simple microscope or magnifier, produces the final image, which is enlarged and virtual.'

The NCERT states: 'Clearly, the final image is inverted with respect to the original object.'