Question

3) The focal length of combination of convex lens of power 1 D and concave lens of power -1.5 D is ......................... (1 mark) *
-2 m
2 m
2.5 m
0.5 m​

Answer 1

Answer:

0.5m

Explanation:

Net power becomes 2D.

We know power =1/f

F=1/P

F=1/2D

F=0.5m.

So the light coming parallel will fall on the new focus I.e. +0.5m.

Answer 2

so, according to question,we know that power= 1/Focal length in meters .so Focal length is 1/power /-0.5=-2meters .But Focal length can't be nagative,so the Focal length is 2 metrs.