Question

Given below are two statements : One is labelled as Assertion $A$ and the other is labelled as reason $R$.

$A$ : For a simple microscope, the angular size of the object equals the angular size of the image.

$R$ : Magnification is achieved as the small object can be kept much closer to the eye than $25\text{cm}$ and hence it subtends a large angle.

In the light of the above statements, choose the most appropriate answer from the options given below.

• A. Both $A$ and $R$ are true, but $R$ is NOT the correct explanation of $A$.
• B. Both $A$ and $R$ are true, and $R$ is the correct explanation of $A$.
• C. $A$ is true, but $R$ is false.
• D. $A$ is false, but $R$ is true.

Answer 1

The correct option is A Both $A$ and $R$ are true, but $R$ is NOT the correct explanation of $A$.

When object is placed at $D=25\text{cm}$,
${\theta }_o=\frac{h}{D}$


When a simple microscope is used,

From the ray diagram, we can see that, the angular size of the object equals the angular size of the image$(=\theta )$.

Also, $\theta =\frac{h}{u_o}$

This angle is greater than ${\theta }_o$ and $u_o<25\text{cm}$.

Hence, magnification is achieved as the small object can be kept much closer to the eye than $25\text{cm}$ and hence it subtends a large angle.

Therefore, both $A$ and $R$ are true, but $R$ is NOT the correct explanation of $A$.