when an object is placed at distance of 10 cm from a convex lens its virtual image twice as big - Science - Light - Reflection and Refraction

Question

​​when an object is placed at distance of 10 cm from a
convex lens its virtual image twice as big as the object is formed
calculate the focal length of the lens where to the object should
the in front of the same lens so as to form its real image of twice
the size

Vijaya Nittala · Accepted Answer

Dear student,
We use formula of magnification for convex lens

given m = 2, u = 10 cm
m = -(-v)u 2 = v10 v = 20 cm
For virtual image v is positive
Calculation for Focal length:
1f=1-20+110f= 20 cm 
To get real inverted image object should be placed beyond its focal
length
m = -vu= -2Here m is negative for the inverted image

1f=12u+1u120=12u+1uu = 30 cm
Regards
Vijaya

​​when an object is placed at distance of 10 cm from a convex lens its virtual image twice as big as the object is formed calculate the focal length of the lens where to the object should the in front of the same lens so as to form its real image of twice the size

when an object is placed at distance of 10 cm from a convex lens its virtual image twice as big as the object is formed calculate the focal length of the lens where to the object should the in front of the same lens so as to form its real image of twice the size