What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20cm- Is the system a converging or a diverging lens- Ignore thickness of the lenses-

Question

Toppr Admin · Accepted Answer

Focal length of convex lenses- f1-30cmFocal length of concave lenses- f2-x2212-20cm-x21D2-1f-1f1-1f2f-x2212-60cm- Therefore diverging lens -

What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.

Focal length of convex lenses, $f_{1} = 30 c m$
Focal length of concave lenses, $f_{2} = - 20 c m$
$\Rightarrow \frac{1}{f} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$
$f = - 60 c m$ . Therefore diverging lens .

What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.

Focal length of convex lenses, f1=30cmFocal length of concave lenses, f2=−20cm⇒1f=1f1+1f2f=−60cm. Therefore diverging lens .

Focal length of convex lenses, $f_{1} = 30 c m$
Focal length of concave lenses, $f_{2} = - 20 c m$
$\Rightarrow \frac{1}{f} = \frac{1}{f_{1}} + \frac{1}{f_{2}}$
$f = - 60 c m$ . Therefore diverging lens .