When an object is placed 10 cm (0.10m) from a converging lens, the real image fo

Question

When an object is placed 10 cm (0.10m) from a converging lens, the real image form is twice the size of the object. What is the power of this lens? 6.7 D 10 D 15 D 20 D Two converging lens are placed in contact If one has a focal length of 10 cm, and the other has a focal length of 20 cm, what is the power of the combination 10 D 15 D 20 D 30 D We view an object at various distances using a mirror with focal length 12 m. (See figure.) If the object is 6m in front of the mirror, where is the image? 6 m in front of the mirror. 6 m behind the mirror 12 m in front of the mirror. 12 m behind the mirror. If the object is 6 m in front of the mirror, what is its magnification? It is half as large, and the image is upright It is half as large, and the image is inverted. It is twice as large, and the image is upright It is twice as large, and the image is inverted If the object is 24 m away from the mirror, where is the image? 12 m in front of the mirror. 12 m behind the mirror. 24 m in front of the mirror. 24 m behind the mirror

Explanation / Answer

(8)
do = 0.1 cm
M = 2 = -di/d0
di = - 2*0.1 = - 0.2

We know,
1/f = 1/di + 1/do
P = -1/0.2 + 1/0.1
P = 5 D

(9)
The combined focal length f of the lenses is given by, 1/f = 1/f1 + 1/f2
P = 1/0.1 + 1/0.2
P = 15 D

(10)
f = 12 m
do = 6 m
1/f = 1/di + 1/do
1/12 = 1/di + 1/6
di = - 12 cm
The image is 12 m behind the mirror.

(11)
M = -di/do
M = 12/6
M = 2
It's twice as large and image is upright !!

(12)
f = 12 m
do = 24 m
1/f = 1/di + 1/do
1/12 = 1/di + 1/24
di = 24 cm
The image is 24 m infront of the mirror.

please post seperate questions in seperate post only.

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