1. An object of height 3.2 cm is placed 30 cm from a convex mirror of focal leng
ID: 1702678 • Letter: 1
Question
1. An object of height 3.2 cm is placed 30 cm from a convex mirror of focal length having magnitude 25 cm.(a) Find the location of the image. (Use a negative value if the image is behind the mirror.) ____ cm
(b) Describe the properties of the image.
height of image = ____ cm
2. An object is placed 74 cm from a concave mirror of radius 11 cm.
(a) Find the location of the image. (Enter in cm. Use a negative number if the image is behind the mirror) =____ cm
(b) What is the magnification of the mirror?
Explanation / Answer
1) Givem height of the object h_o = 3.2 cm
object distance of the lens d_O = 30 cm
focal length of the mirror f = 25 cm
location of the image is calculated by using the mirror equation
mirror equation is
1/ d_o + 1 / d_i = 1 / f
1 / 30 cm + 1 / d_i = 1 / 25 cm
1 / d_i = 1 / 25 cm - 1 / 30 cm
d_i = 150 cm
magnification of the lens M = - d_i / d_o
= 150 cm / 30cm = 5
heigth of the image h_i = - 5*3.2cm = -16 cm
here negative sign represents inverted image
2) object distance of the concave moirror is d_O = 74 cm
radius of concave mirror is R = 11 cm
focal length of concave mirror is f = - R / 2
= -11 /2 = 5.5 cm
mirror equation is
1/ d_o + 1 / d_i = 1 / f
1 / 74cm + 1 / d_i = -1 / 5.5 cm
1 / d_i = -1 / 5.5 cm - 1 / 74 cm
d_i = -5.11cm
magnification M = - d_i / d_o
= 5.11 / 74 = 0.069
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