In: Physics
When two plane mirrors are parallel, such as on opposite walls in a barber shop, multiple images arise because each image in one mirror serves as an object for the other mirror. An object is placed between parallel mirrors separated by 25 cm. The object is 15 cm in front of the left mirror and 10 cm in front of the right mirror.
(a) Find the distance from the left mirror to the first four
images in that mirror.
__cm (image 1)
__cm (image 2)
__cm (image 3)
__cm (image 4)
(b) Find the distance from the right mirror to the first four
images in that mirror.
__cm (image 1)
__cm (image 2)
__cm (image 3)
__cm (image 4)
(c) Explain why each more distant image becomes fainter and
fainter. (Do this on paper. Your instructor may ask you to turn in
your work.)
Distance between mirrors D = 25 cm
Object distance from left mirror = 15 cm
Object distance from right mirror = 10 cm
For plane mirror,
Object distance = -Image distance
Image formed by plane mirror is virtual , so we take minus sign, but here we will ignore sign and just see magnitude
First image distance from Left mirror IL1 = 15 cm
First image distance from Right mirror IR1 = 10 cm
Fisrt image from right mirror acts as object for Left mirror
Second image on Left mirror IL2 = Mirror distance + IR1 = 25cm + 10cm = 35cm
Second image on Right mirror IR2 = 25cm + IL1 = 25cm + 15cm = 40cm
Third Image on Left mirror IL3 = 25cm + IR2 = 25cm + 40cm = 65cm
Third Image on Right mirror IR3 = 25cm + IL2 = 25cm + 35cm = 60 cm
Fourth Image on Left mirror IL4 = 25cm + IR3 = 25cm + 60cm = 85cm
Fourth Image on Right mirror IR4 = 25cm + IL3 = 25cm + 65cm = 90 cm
(a) Distance from left mirror to first four images
IL1 = 15cm . IL2 = 35cm, IL3 = 65cm, IL4 = 85cm
(b) Distance from right mirror to first four images
IR1 = 10cm, IR2 = 40cm, IR3 = 60cm . IR4 = 90cm
(c) Intensity of Light is inversely proportional to Distance square
Thus the distant image becomes fainter and fainter.