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A point source of light S is placed on t...

A point source of light S is placed on the axis of a lens of focal length 20cm at a distance 25cm from lense. A screen is placed normal to the axis of lens at a distance x from it (treat all rays as paraxial). Identify the true or false statements.
a. As x is increased from zero , intensity continuously decreases.
b. As x is increased from zero, intensity first increases then decreases.
c. Intensity at center of screen for `x =90 cm` and `x=110 cm` is same.

A

As x is increased from zero, intensity continuously decreases

B

As x is increased from zero, intensity first increases and then decreases

C

Intensity at centre of screen for `x=90cm`and `x = 110cm` is same

D

radius of bright circle obtained on screen is equal to1cm for `x=200 cm`

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  • An object of height 1.5 cm is placed on the axis of a convex lens of focal length 25 cm . A real image is formed at a distance of 75 cm from the lens. The size of the image will be

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    B
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    C
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    D
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  • An object is placed at a distance of 15 cm from a convex lens of focal length 10 cm. The image obtained on the screen is :

    A
    upright and magnified
    B
    inverted and magnified
    C
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    D
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