Which of the following statements are correct?
(A) In dispersion through a prism of glass, the red colour ray deviates most.
(B) In simple microscope, to get a magnified image, the object is placed within the focus of a convex lens.
(C) In compound microscope, total magnification is m = (magnification due to eye lens) × (magnification due to objective)
(D) magnifying power of telescope M = focal length of eye lens / focal length of objective lens
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) and (C) only
(A) In dispersion through a prism of glass, the red colour ray deviates most. — Incorrect. The refractive index of glass is largest for violet and smallest for red, so violet deviates most and red least.
(B) In simple microscope, to get a magnified image, the object is placed within the focus of a convex lens. — Correct. An object between the lens and its focus gives a virtual, erect and magnified image on the same side, which is how a simple microscope works.
(C) In compound microscope, total magnification is m = (magnification due to eye lens) × (magnification due to objective) — Correct. The eyepiece magnifies the objective’s image again, so the total magnification is the product \( m = m_o\,m_e \).
(D) magnifying power of telescope M = focal length of eye lens / focal length of objective lens — Incorrect. The ratio is inverted. For normal adjustment the magnifying power of a telescope is
\( \displaystyle M = \frac{f_o}{f_e} \)
so a telescope has an objective of long focal length and an eyepiece of short focal length.
Note: Statements (B), (C) and (D) of this question are from the latest textbook (2026-27). Statement (A), on which colour a glass prism deviates most, is printed only in the pre-rationalised textbook (2022-23). It was removed from the latest book, but dispersion of light through a prism is still in the CUET 2026 syllabus, so do not skip it.
NCERT (2026-27):
The Microscope – “A simple magnifier or microscope is a converging lens of small focal length …. In order to use such a lens as a microscope, the lens is held near the object, one focal length away or less, and the eye is positioned close to the lens on the other side.”
The Microscope – “… Thus, the total magnification [(according to Eq. (9.33)], when the image is formed at infinity, is
\( \displaystyle m = m_o m_e = \left(\frac{L}{f_o}\right)\left(\frac{D}{f_e}\right) \qquad (9.45) \)”
Telescope – “… The magnifying power m is the ratio of the angle β subtended at the eye by the final image to the angle α which the object subtends at the lens or the eye. Hence
\( \displaystyle m \approx \frac{\beta}{\alpha} \approx \frac{h}{f_e} \cdot \frac{f_o}{h} = \frac{f_o}{f_e} \qquad (9.46) \)”
NCERT (Pre-rationalised edition, 2022-23):
Dispersion by a Prism – “… The red light bends the least, while the violet light bends the most ….”