Question

An object is placed 25.0 cm in front of a concave mirror of focal length
20.0 cm. At what distance from the mirror should a screen be placed in order
to obtain a sharp image? What is the nature of the image ?​

Answer 1

Answer:the image distance is -100. Thr nature of image is real and inverted.

Explanation:let, u be the object distance =-25 cm

v be the image distance

f be the focal length =-20 cm

According to mirror formula, 1/v=1/f-1/u

=1/20+1/25=-1/100

v=-100cm

Answer 2

Answer:

The screen should be placed 100 cm from the mirror. The image formed is real, inverted, and on the same side as the object.

Explanation:

In this question we are required to apply the mirror formula.

The mirror formula is given by:

1/f = 1/u + 1/v

Here, v = image distance, f = the focal length, and u = the object distance

From the question, we have that:

f = 20 cm

u = 25 cm

So, we need the image distance.

Doing the substitution we have:

1/20 = 1/25 + 1/v

1/v = 1/20 - 1/25 = 1/100

Therefore, v = 100 cm

The image distance is 100 cm

Since the image distance is positive the nature is the image is:

• Real
• Inverted
• Same side as the object