John's Face Is 20 Cm in Front of a Concave

question 74

Multiple Choice

John's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and erect, what is the focal length of the mirror?

• A) 10 cm
• B) 20 cm
• C) 30 cm
• D) 40 cm
• E) 50 cm

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