The focal lengths of the objective and eye-lens of a microscope are 1 cm and 5 cm respectively. If the magnifying power for the relaxed eye is 45, then the length of the tube is

Question

The focal lengths of the objective and eye-lens of a microscope are 1 cm and 5 cm respectively. If the magnifying power for the relaxed eye is 45, then the length of the tube is (A) 30 cm (B) 25 cm (C) 15 cm (D) 12 cm

Tardigrade Admin · Accepted Answer

By using m∞=((L∞-fo-fe) ⋅ D/fo × fe) ⇒ 45=((L∞-1-5) × 25/1 × 5) ⇒ L∞=15 cm

Q. The focal lengths of the objective and eye-lens of a microscope are $1 c m$ and $5 c m$ respectively. If the magnifying power for the relaxed eye is $45$ , then the length of the tube is

30 cm

25 cm

15 cm

12 cm

By using $m_{\infty} = \frac{( L _{\infty} - f _{o} - f _{e} ) \cdot D}{f _{o} \times f _{e}}$
$\Rightarrow 45 = \frac{( L _{\infty} - 1 - 5 ) \times 25}{1 \times 5}$
$\Rightarrow L_{\infty} = 15 c m$

Q. The focal lengths of the objective and eye-lens of a microscope are 1cm and 5cm respectively. If the magnifying power for the relaxed eye is 45, then the length of the tube is