# 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 $$\mu_1$$ and $$\mu_2$$ and $$R$$ is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is: 1. $$\dfrac{R}{2(\mu_1-\mu_2)}$$ 2. $$\dfrac{R}{(\mu_1-\mu_2)}$$ 3. $$\dfrac{2R}{(\mu_2-\mu_1)}$$ 4. $$\dfrac{R}{2(\mu_1+\mu_2)}$$

Subtopic:  Lens Makers' Formula |
66%
From NCERT
AIPMT - 2013
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For a normal eye, the cornea of the eye provides a converging power of $$40~\text{D}$$ and the least converging power of the eye lens behind the cornea is $$20~\text{D}$$. Using this information, the distance between the retina and the cornea-eye lens can be estimated to be:
1. $$2.5~\text{cm}$$
2. $$1.67~\text{cm}$$
3. $$1.5~\text{cm}$$
4. $$5~\text{cm}$$

Subtopic:  Human Eye |
62%
From NCERT
AIPMT - 2013
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When a biconvex lens of glass having a refractive index of $$1.47$$ is dipped in a liquid, it acts as a plane sheet of glass. The liquid must have a refractive index:

 1 equal to that of glass. 2 less than one. 3 greater than that of glass. 4 less than that of glass.
Subtopic:  Lens Makers' Formula |
79%
From NCERT
AIPMT - 2012
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A ray of light is incident at an angle of incidence, $$i$$, on one face of a prism of angle $$A$$ (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is $$\mu,$$ the angle of incidence $$i$$, is nearly equal to:
1. $$\mu A$$
2. $$\frac{\mu A}{2}$$
3. $$\frac{A}{\mu}$$
4. $$\frac{A}{2\mu}$$

Subtopic:  Prisms |
78%
From NCERT
AIPMT - 2012
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A concave mirror of the focal length $$f_1$$ is placed at a distance of $$d$$ from a convex lens of focal length $$f_2$$${}_{}$. A beam of light coming from infinity and falling on this convex lens-concave mirror combination returns to infinity. The distance $$d$$ must be equal to:
1. $$f_1+f_2$$
2. $$-f_1+f_2$$
3. $$2f_1+f_2$$
4. $$-2f_1+f_2$$

Subtopic:  Reflection at Spherical Surface |
From NCERT
AIPMT - 2012
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The magnifying power of a telescope is $$9$$. When it is adjusted for parallel rays the distance between the objective and eyepiece is $$20~\text{cm}$$. The focal length of the lenses is:
1. $$10~\text{cm}, ~10~\text{cm}$$
2. $$15~\text{cm}, ~5~\text{cm}$$
3. $$18~\text{cm}, ~2~\text{cm}$$
4. $$11~\text{cm}, ~9~\text{cm}$$

Subtopic:  Telescope |
82%
From NCERT
AIPMT - 2012
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A biconvex lens $$(\mu=1.5)$$  has a radius of curvature of magnitude $$20~\text{cm}$$. Which one of the following options, best describes, the image formed by an object of height $$2$$ cm placed $$30~\text{cm}$$ from the lens?
 1 virtual, upright, height $$=0.5$$ cm 2 real, inverted, height $$=4$$ cm 3 real, inverted, height $$=1$$ cm 4 virtual, upright, height $$=1$$ cm
Subtopic:  Lenses | Lens Makers' Formula | Refraction at Curved Surface |
70%
From NCERT
AIPMT - 2011
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Which of the following is not due to total internal reflection?

 1 Difference between apparent and real depth of the pond 2 Mirage on hot summer days 3 Brilliance of the diamond 4 Working of optical fibre
Subtopic:  Total Internal Reflection |
85%
From NCERT
AIPMT - 2011
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A ray of light travelling in a transparent medium of refractive index $$\mu$$ falls on a surface separating the medium from the air at an angle of incidence of $$45^{\circ}$$. For which of the following value of $$\mu$$, the ray can undergo total internal reflection?
1. $$\mu = 1.33$$
2. $$\mu =1.40$$
3. $$\mu=1.50$$
4. $$\mu = 1.25$$

Subtopic:  Total Internal Reflection |
63%
From NCERT
AIPMT - 2010
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A lens having focal length $$f$$ and aperture of diameter $$d$$ forms an image of intensity $$I$$. An aperture of diameter $$\frac{d}{2}$$ in central region of lens is covered by a black paper. The focal length of lens and intensity of the image now will be respectively:
1. $$f$$ and $$\frac{I}{4}$$
2. $$\frac{3f}{4}$$ and $$\frac{I}{2}$$
3. $$f$$ and $$\frac{3I}{4}$$
4. $$\frac{f}{2}$$ and $$\frac{I}{2}$$

Subtopic:  Lenses |
57%
From NCERT
AIPMT - 2010
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