2. A concave mirror with a focal length of 10.0 cm creates a real image 30.0 cm

Question

2. A concave mirror with a focal length of 10.0 cm creates a real image 30.0 cm away on its principal axis. How far from the mirror is the corresponding object?

A) 7.50 cm

B) 20.0 cm

C) 5.00 cm

D) 15.0 cm

4. An object is placed along the principal axis of a thin converging lens that has a focal length of 30.0 cm. If the distance from the object to the lens is 40.0 cm, what is the distance from the image to the lens?

A) –17.3 cm

B) –1.20 m

C) 1.20 m

D) 17.3 cm

5. If a virtual image is formed 10.0 cm along the principal axis from a convex mirror with a focal length of – 15.0 cm, what is the object’s distance from the mirror?

A) 12 cm

B) 6.0 cm

C) 3.0 cm

D) 30.0 cm

6. Which best describes the image of a concave mirror when the object is at a distance greater than twice the focal-point distance from the mirror?

A) real, inverted, and magnification less than one

B) virtual, upright, and magnification less than one

C) real, inverted, and magnification greater than one

D) virtual, upright, and magnification greater than one

Explanation / Answer

2) F=-10cm

1/u +1/v=1/(-10)

as the object and image are on the same side both are negative

so in this case leaving negative sign we left with 1/u +1/v=1/(10)

1/u=1/10-1/30

calculating u=15cm option D is correct

4)using 1/v+1/u=1/f for converging lens and substituting u=40cm and f=30cm we will get the value of v=120cm =1.2m so optionCis correct.

5)using 1/v+1/u=1/f for convex mirror and substituting v=10cm and f=15cm we will get the value of u=30cm so option D is correct.

6)in this case option C is correct

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