Question

The focal length of a convex lens is 3cm. Draw the ray diagram of an object placed on the principal axis

Answer 1

Answer:

Explanation:

h  

1

​  

=1cm, u=-30cm,f=20cm, h  

2

​  

=?, v=?

v

1

​  

+  

u

1

​  

=  

f

1

​  

 

$$\displaystyle \Rightarrow \frac{1}{v}+\frac{1}{\left

(-30  \right )}=\frac{1}{20}$$

$$\displaystyle \Rightarrow

\frac{1}{v}=\frac{1}{30}+\frac{1}{20}$$

∴v=12cm

The image is formed 12cm behind the mirror.

m=−  

u

v

​  

=  

h  

1

​  

 

h  

2

​  

 

​  

 

m=−  

−30

12

​  

=  

1

h  

2

​  

 

​  

 

h  

2

​  

=0.4cm