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WorksheetsMirror & Lens Formula
Total questions: 10
Worksheet time: 34mins
A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.
u=-60; h' =(5/4)
u=-60; h' =(4/5)
u= +60; h' =(5/4)
u=+60; h' =(4/5)
A concave mirror of focal length 20 cm forms an image having twice the size of object. For the virtual position of object, the position of object will be at:
25 cm
40 cm
10 cm
At infinity
If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be:
75 cm
25 cm
15 cm
60 cm
The refractive index of water is 1.33. The speed of light in water will be:
1.33 × 10^8 m/s
3 × 10^8 m/s
2.66 × 10^8 m/s
2.26 × 10^8 m/s
You are given three media A, B and C of refractive index 1.33, 1.65 and 1.46. The medium in which the light will travel fastest is
A
B
C
Equal in all media
A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is
-10 cm
20 cm
-30 cm
-40 cm
Which of the following statements is/are 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 having a focal 0.25 m
A point object is placed at a distance of 20 cm from a convex mirror of focal length 20 cm. The image will form at:
at infinity
at focus
at pole
behind the mirror.
If the power of a lens is – 2 D, what is its focal length?
+50 cm
-100 cm
-50 cm
+100 cm
A ray of light is travelling from a rarer medium to a denser medium. While entering the denser medium at the point of incidence, it:
goes straight into the second medium
bends towards the normal
bends away from the normal
does not enter at all
