Question

A dancer is applying make-up using a concave mirror. The dancer's face is 35 cm in

front of the mirror, and the image is 72 cm behind the mirror. Use the mirror
equation to calculate the focal length of the mirror.

Answer 1

The focal length of the concave mirror is -72 cm.

Step-by-step explanation:

The focal length of the mirror can be calculated using the mirror equation. The formula for the mirror equation is 1/f = 1/di + 1/do, where f is the focal length, di is the image distance, and do is the object distance.

In this case, the object distance (do) is 35 cm and the image distance (di) is -72 cm (negative because the image is formed behind the mirror). Plugging these values into the mirror equation:

1/f = 1/-72 + 1/35

Now, we can solve for f:

1/f = -35/2520

f = -2520/35

f = -72 cm

Answer 2

Step-by-step explanation:

u = -35

v = +72(behind the mirror)

1/f = (1/u)+(1/v)

1/f = (1/72)- (1/35)

1/f = {(35-72)}/2520

1/f = -37/2520

1/f = -1/68.11

f = -68.11cm .