wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

Two thin lenses of power +2.0D and -1.5D are placed in contact. Find the a. power and b. focal length of the combination of lenses. c. Also state the nature of the lens formed by the combination of these lenses.


Open in App
Solution

Step 1 - Given data.

Let the power of lens 1 be P1=+2.0D.
Let the power of lens 2 be P2=-1.5D.

Step 2 - Formula Used.
The formula for calculating the total power is P=P1+P2.
The focal length (f) of the combination of lenses can be found using the formula for power which is given as: P=1f. Therefore, f=1P.

Step 3 - Finding the total power.

Substitute the values into the formula to calculate the total power.

P=P1+P2P=+2.0-1.5P=0.5D

Step 4 - Finding the focal length of the combination of lenses.

Substitute the values into the formula for power to calculate the focal length of the combination of lenses.

f=1Pf=10.5Df=2mf=+200cm

(Note:- m-1=D and1m=100cm)

Since the focal length of the combination of lenses is positive, the two lenses together act as a converging(convex) lens.


a. The total power is 0.5D.
b. The focal length of the combination of the lenses is +200cm.
c. The two lenses together act as a converging(convex) lens.


flag
Suggest Corrections
thumbs-up
9
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Total Internal Reflection
PHYSICS
Watch in App
Join BYJU'S Learning Program
CrossIcon