Test Series-17

## Instructions

• Your test contains 12 multiple choice questions with only one answer
• This is 30 min test.Please make sure you complete it in stipulated time
• You can Finish this test any time using 'Submit' button.
• Once finished you get a chance to review all question with correct answers and their solutions.

1.Which of these is false for refractive index?
• It has no units
• The lights rays bends more in glass then in water
• it depends on the nature of the medium
• It depends on the angle of the incidence
• None of these

A convex lens X and A convex lens Y of focal lenght 10 cm and 25 cm are placed in close contact with one other.
2) What is the unit of Power of the lens?
• Dioptres
• No units
• None of these

3. What is power of the this combination
• 14
• 6
• 1
• None of these

4..What is focal length of this combination?
• 7.1cm
• 35cm
• 5 cm
• None of these

5.Two medium X and Y with refractive index 1.31 and 1.50 are given.?Which of the following is false
• Y will bend the light more
• Speed of the light will be more in X
• None of these

6. The refractive index of glass with respect to water is 1.22. The refractive index of glass with respect to air is 1.5 What will be the refractive index of water with respect to air?
• 1.2
• 1.9
• 1.6
• 1.33
• None of these

7. A convex lens has a focal length of 30 cm. Calculate at what distance should the object be placed from the lens so that it forms an image at 60 cm on the other side of the lens?
• 25cm
• 60cm
• 30cm
• None of these

8. Concave lens always provide?
• Inverted and diminished image
• erect and magnified images
• Erect and diminished image
• None of these

9.Where should an object be placed, so that a real and inverted image of the same size is obtained by a  Convex lens?
• at the focus of the lens
• at twice the focal length
• at infinity
• between the optical centre of the lens and its focus

10.The power of the lens is +2.5D. What is the nature and focal lenght of the lens?
• Concave,20 cm
• Convex,20 cm
• Concave,40 cm
• Convex,40 cm

11. The focal length and power of the combination of convex and concave lens of same focal lenght placed in contact with each other?
• half the focal length,twice the power of single lens
• zero,infinite
• infinite,zero
• twice the focal lenght of single lens and half the power of single lens

12. A object of lenght 4cm is placed at a distance 20cm from a convex lens of focal length 10 cm. What is the lenght and nature of the image?
• 4cm ,inverted real
• 2cm ,inverted real
• 4cm ,inverted virtual
• 2cm,inverted virtual

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