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WorksheetsLens
Total questions: 15
Worksheet time: 9mins
We combine two lenses, one is convex and other is concave having focal lengths /, and f2 and their combined focal length is F. Combination of the lenses will behave like concave lens, if
f1 > f2
f1 = f2
f1 < f2.
f1 ≤ f2
We combine two lenses, one is convex and other is concave having focal lengths /, and f2 and their combined focal length is F. Combination of the lenses will behave like concave lens, if
f1 > f2
f1 = f2
f1 < f2.
f1 ≤ f2
A convex lens and a concave lens, each having the same focal length of 25 cm, are put in contact to form a combination of lenses. The power of the combination (in dioptres) is
zero
25
50
infinity
Which of the following statements is true ?
A convex lens has 4 dioptre power having a focal length 0.25 m
A convex lens has -4 dioptre power having a focal length 0.25 m
A concave lens has 4 dioptre power having a focal length 0.25 m
A concave lens has -4 dioptre power having a focal length 0.25 m.
A convex and a concave lens of equal focal length behaves as a regular glass slab receiving light normally.
True
False
If magnification is less than one (m<1) then the size of the image is
Enlarged
Diminished
Same size as object
The power of a lens is -5D. Find its focal length
20 cm
20 m
-20cm
-20mm
A 6cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 25 cm. The object distance is 40 cm, find the image distance and magnification.
V= 200/3 cm
V= 400/13 cm
m= 10 cm
m= -10 cm
The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?
f = 40 cm .
The lens is convex and image formed at 80 cm from the lens is real and inverted.
f = 20 cm .
The lens is concave and image formed at 80 cm from the lens is real and inverted.
f = 20 cm .
The lens is convex and image formed at 80 cm from the lens is real and inverted.
f = 40 cm .
The lens is concave and image formed at 80 cm from the lens is real and inverted.
The unit of Power of a lens
Dioptre
Meter
Kilogram
Newton
The power of a convex lens of focal length 50 cm is .
+ 2D
- 2D
50 D
- 5D
The ratio of height of image to height of the object is
Magnification
Power of a lens
Lateral displacement
Focal length
Where should an object be placed in front of a convex lens to get a real image of the size of the object?
At infinity
At twice the focal length
At principal focus of the lens
None
A combination of two convex lenses has a focal length of 20 cm. If the focal length of one of the lenses is 60 cm, what is the focal length of the other?
30 cm
40 cm
20 cm
60 cm
