A thin convex lens made from crown glass μ = 3 2 has focal length f ⁡ . When it is measured in two different liquids having refractive indices 4 3 and 5 3 , it has the focal lengths f ⁡ 1 and f ⁡ 2 respectively. The correct relation between the focal lengths is :

f ⁡ 1 > f ⁡ and f ⁡ 2 becomes negative

f ⁡ 2 > f ⁡ and f ⁡ 1 becomes negative

f ⁡ 1 and f ⁡ 2 both become negative

Numerical aperture of an optical fiber is a measure of

light gathering power of the fiber

attenuation of light signals in the fiber

difference between the refractive indices of core and the cladding

A concave glass lens of refractive index 1 . 5 is immersed in carbon di-sulfide (refractive index = 1 . 6 ). Which of the following is true? [ Assume both surfaces of the lens have same radius of curvature = R ]

It will behave as convergent lens with focal length 8 R

It will behave as divergent lens with focal length 8 R

It will behave as convergent lens with focal length 7 . 5 R

It will behave as divergent lens with focal length 7 . 5 R

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The graph shows how the magnification $m$ produced by a thin lens varies with image distance $v$ . The focal length of the lens used is

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Important Questions on Ray Optics

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 45

A thin convex lens made from crown glass

(μ = \frac{3}{2})

has focal length

f

. When it is measured in two different liquids having refractive indices

\frac{4}{3}

and

\frac{5}{3}

, it has the focal lengths

f_{1}

and

f_{2}

respectively. The correct relation between the focal lengths is :

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 46

In an experiment a convex lens of focal length

15 cm

is placed coaxially on an optical bench in front of a convex mirror at a distance of

5 cm

from it. It is found that an object and its image coincide, if the object is placed at a distance of

20 cm

from the lens. The focal length of the convex mirror is-

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 47

A thin lens made of glass (refractive index

= 1.5

) of focal length

f = 16 c m

is immersed in a liquid of refractive index

1.42

. If its focal length in liquid is

f_{l}

, then the ratio

f_{l} / f

is closest to the integer:

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 48

A plano - convex lens (focal length

f_{2}

, refractive index

μ_{2},

radius of curvature R) fits exactly into a plano - concave lens (focal length

f_{1},

refractive index

μ_{1},

radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be:

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 49

Formation of real image using a biconvex lens is shown below:

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If the whole set up is immersed in water without disturbing the object and the screen positions, what will one observe on the screen?

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 50

A double convex lens has power

P

and same radii of curvature

r

of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power

1.5 P

is :

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 51

The position of the final image formed by the given lens combination from the third lens will be at a distance of $(f_{1} = + 10 cm, f_{2} = - 10 cm$ and $f_{3} = + 30 cm)$

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Physics Crash Course NEET>Chapter 17 - Ray Optics>Level 2>Q 52

A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices

μ_{1}

and

μ_{2}, R

is the radius of curvature of the curved surface of the lenses, then the focal length of combination is

The graph shows how the magnification m produced by a thin lens varies with image distance v. The focal length of the lens used is

Important Questions on Ray Optics

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The graph shows how the magnification $m$ produced by a thin lens varies with image distance $v$ . The focal length of the lens used is