Question

Some rays falling on a converging lens are focused 20 cm from the lens. When a diverging lens is placed in contact with the converging lens, the rays are focused 30 cm from the combination. What is the focal length of the diverging lens?

Answer 1

focused 20 cm from the lens. When a

diverging lens is placed in contact with the

converging lens, the rays are for 30 cm from

the combination. What is the focal length of

the diverging lens.

(a)50cm

(b)-50cm

(c)-60cm

(d60cm

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Answer 2

Answer:

f1=20cm f1+f2=30cm

we know that the focal length of combination of lens f=f1+f2+f3+f4+.............+fn

Explanation:

so by using this concept f=30cm

f1+f2=30cm now f1 =20cm hence f2 =30-20=10cm