Question

when an object is placed 20cm from a concave mirror a real image magnified three times is formed find the image distance and focal length​

Answer 1

Answer:

as we know that concave mirror is toward the center of sphere sp that object distance u is negative

u= -20cm

m=3

v÷u=3

-v÷(-20)=3

-v=3×-20

v=60

as we know image is real so that image distance is positive

by using mirror formula

1/f=1/v+1/u

1/f=1/60+1/-20

taking lcm

1/f=1/60-1/20

1/f=1-3/60

1/f= -2/60

1/f =-1/30

by doing reciprocal

f=-30