Question

A concave mirror has a 7.0 cm focal length. A 2.4 cm tall object is 16.0 cm from the mirror. Determine the image height

Answer 1

Concept:

• Concave mirror
• mirror formula
• Reflection
• Sign conventions for curved mirrors
• A mirror that has a curved reflecting surface is said to be curved.
• The surface could be concave or convex.
• The majority of curved mirrors have surfaces that resemble a sphere.

Given:

• The focal length of concave mirror f = 7.0 cm
• Object distance u = -16.0 cm
• Object height h = 2.4 cm

Find:

• The image height h'

Solution:

We know the mirror formula

1/f = 1/v + 1/u

1/7 = 1/v -1/16

1/7 + 1/16 = 1/v

1/v = 23/112

v = 4.87 cm

We know the magnification formula

m = -v/u = h'/h

h'/h = 4.87/16

h' = 4.87/16 * 2.4 = 0.73 cm

The image height is 0.73 cm.

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