Question

An object 0.006 meters tall is placed 0.2 meters in front of a concave mirror and an image is formed 5 meters in front of the mirror. What is the focal length of the mirror? What is the height of the image?

Answer 1

• $1/f= 1/u + 1/v$ where f is the focal length, u is the object distance and v is the image distance.
• 1/f=1/0.2+1/5
• 1/f = 5.2 meters
• f=1/5.2= 5/26 meters
• For image height we will use magnification formula $hi/ho=di/do=m.$
• 5/0.2=m=25
• 25=hi/0.006
• hi=25 \times 0.006
• hi = 0.15 meters