Physics MCQs for NEET — Practice Questions with Answers

As explained in the NCERT text, such a process, while conserving energy (First Law), is never observed and is forbidden by the Second Law of Thermodynamics because it implies a spontaneous transfer of internal energy from a colder object (table) to provide ordered mechanical work (book jumping).

The NCERT text states: 'Put simply, the Second Law implies that no heat engine can have efficiency $\eta$ equal to 1 or no refrigerator can have co-efficient of performance $\alpha$ equal to infinity.' A 'perfect' engine/refrigerator would achieve these impossible limits.

The NCERT text mentions that 'Spontaneous processes of nature are irreversible.' Combustion is a spontaneous and irreversible chemical process. Ideal gas expansion (if quasi-static) and phase changes at equilibrium are often considered idealized reversible processes, and heat transfer in a vacuum itself doesn't make the entire system reversal without other actions.

According to the NCERT text, 'Such big lenses tend to be very heavy and therefore, difficult to make and support by their edges. Further, it is rather difficult and expensive to make such large sized lenses which form images that are free from any kind of chromatic aberration and distortions.' The 'absence of image inversion' is not listed as a problem associated with the objective lens itself, but rather an issue that terrestrial telescopes address with additional inverting lenses. Refracting telescopes can produce inverted images, but this is a characteristic, not a problem inherent in large objective lenses.

The NCERT text states, 'In this case, the length of the telescope tube is $f_o + f_e$.' This refers to a refracting telescope when the final image is formed at infinity (normal adjustment).

The NCERT text provides an example: 'For example, consider a telescope whose objective has a focal length of 100 cm and the eyepiece a focal length of 1 cm. The magnifying power of this telescope is m = 100/1 = 100.' This directly applies the formula $m = f_o / f_e$.

The NCERT excerpt states, 'The main considerations with an astronomical telescope are its light gathering power and its resolution or resolving power.'

The NCERT text mentions, 'The resolving power, or the ability to observe two objects distinctly... also depends on the diameter of the objective. So, the desirable aim in optical telescopes is to make them with objective of large diameter.'

The NCERT states, 'For these reasons, modern telescopes use a concave mirror rather than a lens for the objective. Telescopes with mirror objectives are called reflecting telescopes. There is no chromatic aberration in a mirror.'

The NCERT text highlights, 'Mechanical support is much less of a problem since a mirror weighs much less than a lens of equivalent optical quality, and can be supported over its entire back surface, not just over its rim.'