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Concave Lens - Focal Length
Concave Lens - Focal Length
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1)
Which one of the following is true about a concave lens?
It has uniform thickness.
It is a converging lens.
It is a diverging lens.
It is thicker at the middle than at the edges.
2)
A diverging lens has a focal length of 10 cm. Where is the image located when an object is placed 30 cm from the lens?
30 cm on the near side.
7.5 cm on the near side.
7.5 cm on the far side.
15 cm on the near side.
3)
An object is 18.6 cm in front of a concave lens. The image is formed at 13 cm from the lens. What is the focal length of the lens?
-43 cm
-10 cm
-50 cm
-41 cm
4)
A concave lens has focal length of -30 cm. It produces an image at 15 cm when the object is placed 10 cm. What is the magnification of the image?
1
1.5
1.2
2
5)
Which one of the following is the correct equation used to calculate the focal length of a concave lens?
1/f = 1/v+1/u
1/f = uv/(u+v)
1/f = 1/v-1/u
f= (u-v)/uv
6)
An object is placed 5 cm from the concave lens. If it produces an image at 6 cm, what is the focal length of the lens?
-30 cm
-40 cm
-60 cm
-50 cm
7)
In lens in contact method, if F is the focal length of the combination of convex lens and liquid and f₁ is the focal length of convex lens. Which one of the following equations is used to calculate the focal length (f₂) of the concave lens?
f₂ = (f₁-F)/Ff₁
f₂ = f/(f₁-F)
f₂ = Ff₁/(f₁-F)
f₂ = F/(F-f₁)
8)
If the focal length of a convex lens is 10 cm and that of a concave lens is -43 cm, what will be the focal length of the combination of lenses?
15 cm
13 cm
10 cm
20 cm
9)
A convex lens has focal length f. An object is placed at 2f on the axis. Where is the image formed located?
Between the lens and f.
At 2f.
At f.
Between f and 2f.
10)
A convex lens has focal length f. An object is placed at infinity. Where is the image formed located?
At 2f.
Between f and 2f.
At f.
Between the lens and f.