Lakshya Education MCQs

Question: An object 2.5 cm high is placed at a distance of 10 cm   from a concave mirror of radius of curvature 30 cm  The size of the image is    
Options:
A.9.2 cm
B.10.5 cm
C.5.6 cm
D.7.5 cm
Answer: Option D
: D

R=-30cm f=-15cm
O=+2.5cm,u=-10cm

By mirror formula 115=1v+1(10)v=20cm.
Also IO=vuI(+2.5)=30(10)I=+7.5cm.

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Question 1. An object 2.5 cm high is placed at a distance of 10 cm   from a concave mirror of radius of curvature 30 cm  The size of the image is
  1.    9.2 cm 
  2.    10.5 cm 
  3.    5.6 cm
  4.    7.5 cm 
Answer: Option D
: D

R=30cmf=15cm
O = +2.5 cm, u =-10 cm
By mirror formula 115=1v+1(10)v=30cm.
Also IO=vuI(+2.5)=30(10)I=7.5cm.
Question 2. A ray incident at an angle 53 on a prism and emerges at an angle of 37 as shown in figure. If the angle of incidence is made 50 then possible value of the angle of emergence is

  1.    35∘
  2.    42∘
  3.    40∘
  4.    38∘
Answer: Option D
: D

Deviation produce by the prism isδ=i+eA=53+37A=90A
For angle of incidence 50 angle of emergence will be grater than 37 and also
i + e < 90
Question 3. The focal length of a concave mirror is f and the distance from the object to the principle focus is x. The ratio of the size of the image to the size of the  object is          

[Kerala PET 2005]
Answer: Option D
: B

Question 4. An object 5 cm tall is placed 1 m from a concave spherical mirror which has a radius of curvature of 20 cm. The height of the image is
  1.    0.11 cm
  2.    0.50 cm
  3.    0.55 cm
  4.    0.60 cm
Answer: Option C
: C

By using IO=ffu
Here O+5cm,f=R2=10cm,u=1m=100cm
So, I+5=1010(100)I=0.55cm.
Question 5. The focal length of a concave mirror is 50cm Where an object be placed so that its image is two times and inverted 
  1.    75cm
  2.    72cm
  3.    63 cm
  4.    50 cm
Answer: Option A
: A


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