Question

Answer the questions below based on the information of the convex lens in the table below

S.no Object distance

u

Image distance

v

1 20cm Infinity

2 30cm 60cm

3 40cm 40cm

4 50cm 33cm

5 60cm 30cm



Choose the correct answers for the following questions given below. 4×½=2M

11) Parallel rays to the principle axis of the convex lens after refraction converge at----

A. )Pole B) Centre of curvature

C) Infinite distance D) Focus

12) The value of least distance of distinct vision is ____

A) 25cm B ) 2.5cm

C) 25m D) 2.5 m

13) Which of the following lenses are used to correct myopia of a person?

A) Biconvex lens B) Biconcave Lens

C) Bifocal lens D) Plano convex lens

14) The relation angle of incidence (i1), angle of emergence (i2), angle of deviation (d) and angle of prism (A) is given

as____

A) d=i1+i2 B). A+d=i1-i2

C) A+d=i1+i2 D) A-d=i1+i2

1) What is the focal length of the lens?

2) When the distance of the object is 50cm, write the

image characteristics

3) What is the distance to the object to obtain the

virtual image?

4) At which distance (U), the height of object is equal

to height of image.​

Answer 1

Answer:

Equivalent focal length is given by,

f

1

​  

=  

f  

1

​  

 

1

​  

+  

f  

2

​  

 

1

​  

 

Here, f  

1

​  

=20cm and f  

2

​  

=−40cm

∴  

f

1

​  

=  

20

1

​  

−  

40

1

​  

=  

40

2−1

​  

⇒f=40cm

∵  

ν

1

​  

−  

u

1

​  

=  

ν

1

​  

−  

∞

1

​  

⇒v=f=40cm

∵[u=∞]

Explanation: