A converging lens (lens 1) with a focal length of +20 cm is located 10 cm to the

Question

A converging lens (lens 1) with a focal length of +20 cm is located 10 cm to the left of a diverging lens (lens 2) having a focal length of -25 cm. If an object is located 30 cm to the left of the converging lens, which of the following statements is true?
The final image formed by the diverging lens is: A. 9. 50 cm to the left of lens 2 and real. B. 50 cm to the left of lens 2 and twice the size of the object. C. real and upright D. 30 cm to the left of lens 2 and half the size of the object. E. upside down and twice the size of the object.

The answer is B... Why?

A converging lens (lens 1) with a focal length of +20 cm is located 10 cm to the left of a diverging lens (lens 2) having a focal length of -25 cm. If an object is located 30 cm to the left of the converging lens, which of the following statements is true?
The final image formed by the diverging lens is: A. 9. 50 cm to the left of lens 2 and real. B. 50 cm to the left of lens 2 and twice the size of the object. C. real and upright D. 30 cm to the left of lens 2 and half the size of the object. E. upside down and twice the size of the object.

The answer is B... Why?

The final image formed by the diverging lens is: A. 9. 50 cm to the left of lens 2 and real. B. 50 cm to the left of lens 2 and twice the size of the object. C. real and upright D. 30 cm to the left of lens 2 and half the size of the object. E. upside down and twice the size of the object.

The answer is B... Why?

Explanation / Answer

f1 = +20 cm

f2 = -25 cm

u1 = -30 cm

So, 1 / v1 - 1 / u1 = 1 / f1

So, v1 = +60 cm

SO, u2 = 60-10 = 50 cm

f2 = -25 cm

So, 1 / v2 - 1 / u2 = 1 / f2

So, v2 = -50 cm

-ve sign means, it is to the left....

Magnification = v1 / u1 * v2 / u2 = (60 * -50) / (-30 * 50 )= 2

Hence B is correct...

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