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: Â Lenses |Â Lens Makers' Formula |Â Refraction at Curved Surface |
Â 70%
From NCERT
AIPMT - 2011
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A converging beam of rays is incident on a diverging lens. Having passed through the lens the rays intersect at a point $$15~\text{cm}$$ from the lens on the opposite side. If the lens is removed the point where the rays meet will move $$5~\text{cm}$$ closer to the lens. The focal length of the lens is:
1.  $$5~\text{cm}$$
2. $$-10~\text{cm}$$
3. $$20~\text{cm}$$
4. $$-30~\text{cm}$$

Subtopic: Â Lenses |
Â 53%
From NCERT
AIPMT - 2011
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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: Â Lenses |
Â 57%
From NCERT
AIPMT - 2010
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Two thin lenses of focal lengths f1 and f2 are in contact and coaxial. The power of the combination is:

1. $\sqrt{\frac{{\mathrm{f}}_{1}}{{\mathrm{f}}_{2}}}$

2. $\sqrt{\frac{{\mathrm{f}}_{2}}{{\mathrm{f}}_{1}}}$

3. $\frac{{\mathrm{f}}_{1}+{\mathrm{f}}_{2}}{{\mathrm{f}}_{1}{\mathrm{f}}_{2}}$

4. None of the above

Subtopic: Â Lenses |
Â 87%
From NCERT
AIPMT - 2008
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A boy is trying to start a fire by focusing sunlight on a piece of paper using an equiconvex lens of a focal length of $$10$$ cm. The diameter of the sun is $$1.39\times10^9$$ m and its mean distance from the earth is $$1.5\times10^{11}$$ m. What is the diameter of the sun's image on the paper?

 1 $$9.2\times10^{-4}$$ m 2 $$6.5\times10^{-4}$$ m 3 $$6.5\times10^{-5}$$ m 4 $$12.4\times10^{-4}$$ m
Subtopic: Â Lenses |
Â 58%
From NCERT
AIPMT - 2008
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A convex lens and a concave lens, each having the same focal length of 25 cm, are put in contact to form a combination of lenses. The power in dioptres of the combination is:

1. 25

2. 50

3. infinite

4. zero

Subtopic: Â Lenses |
Â 59%
From NCERT
AIPMT - 2006
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