If the focal length of objective and eye lens are 1.2 cm and 3 cm respectively and the object is put 1.25 cm away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is :

Question

If the focal length of objective and eye lens are 1.2 cm and 3 cm respectively and the object is put 1.25 cm away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is : (A) 150 (B) 200 (C) 250 (D) 400

Tardigrade Admin · Accepted Answer

m ∞ - ( v 0/ u 0) × ( D / f e ) From (1/ f 0)=(1/ v 0)-(1/ u 0) ⇒ (1/(+1.2))=(1/ v 0)-(1/(-1.25)) ⇒ v 0=30 cm ∴ | m ∞|=(30/1.25) × (25/3)=200

Q. If the focal length of objective and eye lens are $1.2 c m$ and $3 c m$ respectively and the object is put $1.25 c m$ away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is :

150

200

250

400

$m_{\infty} - \frac{v _{0}}{u _{0}} \times \frac{D}{f _{e}}$
From $\frac{1}{f _{0}} = \frac{1}{v _{0}} - \frac{1}{u _{0}}$
$\Rightarrow \frac{1}{( + 1.2 )} = \frac{1}{v _{0}} - \frac{1}{( - 1.25 )}$
$\Rightarrow v_{0} = 30 c m$
$∴ ∣ m_{\infty} ∣ = \frac{30}{1.25} \times \frac{25}{3} = 200$

Q. If the focal length of objective and eye lens are 1.2cm and 3cm respectively and the object is put 1.25cm away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is :

150

200

250

400

m∞​−u0​v0​​×fe​D​ From f0​1​=v0​1​−u0​1​ ⇒(+1.2)1​=v0​1​−(−1.25)1​ ⇒v0​=30cm ∴∣m∞​∣=1.2530​×325​=200

Q. If the focal length of objective and eye lens are $1.2 c m$ and $3 c m$ respectively and the object is put $1.25 c m$ away from the objective lens and the final image is formed at infinity. The magnifying power of the microscope is :

$m_{\infty} - \frac{v _{0}}{u _{0}} \times \frac{D}{f _{e}}$
From $\frac{1}{f _{0}} = \frac{1}{v _{0}} - \frac{1}{u _{0}}$
$\Rightarrow \frac{1}{( + 1.2 )} = \frac{1}{v _{0}} - \frac{1}{( - 1.25 )}$
$\Rightarrow v_{0} = 30 c m$
$∴ ∣ m_{\infty} ∣ = \frac{30}{1.25} \times \frac{25}{3} = 200$