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A candle flame 9.10 cm from a lens produces a real image 13.30 cm from the lens.

ID: 1556098 • Letter: A

Question

A candle flame 9.10 cm from a lens produces a real image 13.30 cm from the lens. The lens has one flat side and one curved side, is made of glass with an index of refraction of 1.52, and is surrounded by air. (a) Calculate the focal is include the lens. Be sure to include the appropriate sign and units. (b) Calculate the radius of curvature of the curved side of the lens. (c) Is the curved side convex or concave? How do you know? An 8.14 mm tall object is 6.72 cm from a convex with a radius of curvature of 4.60 cm. (a Calculate the image distance. Be sure to include the appropriate sign and units. (b) Calculate the image height. Be sure to include the appropriate sign and units. (c) Circle the characteristic of the image. That is, the image is: real upright larger than the object virtual inverted smaller than the object

Explanation / Answer

2)

a)
u = 9.1 cm

v = 13.3 cm


1/f = 1/u + 1/v

1/f = 1/9.1 + 1/13.3

f = 5.4 cm


b)
for the lens, R1 is the radius of curvature of first side

and R2 = infinite

now use Lens makers formula,

1/f = (n - 1)*(1/R1 - 1/R2)

1/5.4 = (1.52 - 1)(1/R1 - 0)

==> R1 = 2.81 cm


c) convex. Because the focal length of the lens is positive.

3)

from the given data

h = 8.14 mm
u = 6.72 cm

f = -R/2 = -4.6/2 = -2.3 cm


a) use, 1/u + 1/v = 1/f

1/v = 1/f - 1/u

1/v = 1/(-2.3) - 1/6.72

v = -1.71 cm

b) magnification, m = -v/u

= -(-1.71)/6.72

= 0.254

image height, h' = m*h

= 0.254*8.14

= 2.07 mm

c) virtual, upright, smaller than the object.