In an astronomical telescope in normal adjustment, a straight line of length \(L\) is drawn on the inside part of the objective lens. The eye-piece forms a real image of this line. The length of this image is \(l.\) The magnification of the telescope is:
1. \(\frac{L}{l}+1\)
2. \(\frac{L}{l}-1\)
3. \(\frac{L+1}{l-1}\)
4. \(\frac{L}{l}\)

Subtopic:  Telescope |
 58%
From NCERT
NEET - 2015
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A beam of light consisting of red, green, and blue colours is incident on a right-angled prism. The refractive index of the material of the prism for the red, green, and blue wavelengths is \(1.39\), \(1.44\), and \(1.47\) respectively. 
  
The prism will:

1. separate the blue colour part from the red and green colour
2. separate all the three colours from one another
3. not separate the three colours at all 
4. separate the red colour part from the green and blue colours
Subtopic:  Prisms |
 62%
From NCERT
NEET - 2015
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Two identical thin plano-convex glass lenses (refractive index = \(1.5\)) each having radius of curvature of \(20\) cm are placed with their convex surfaces in contact at the centre. The intervening space is filled with oil of a refractive index of \(1.7\). The focal length of the combination is:
1. \(-20\) cm
2. \(-25\) cm
3. \(-50\) cm
4. \(50\) cm

Subtopic:  Lens Makers' Formula |
 60%
From NCERT
NEET - 2015
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The refracting angle of a prism is \(A,\) and the refractive index of the material of the prism is \(\text{cot} \frac{A}{2}.\) The angle of minimum deviation is:
1. \(180^\circ-3A\)
2. \(180^\circ-2A\)
3. \(90^\circ-A\)
4. \(180^\circ+2A\)
Subtopic:  Prisms |
 81%
From NCERT
NEET - 2015
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If the focal length of the objective lens is increased then the magnifying power of:

1. microscope will increase but that of the telescope decrease.
2. microscope and telescope both will increase.
3. microscope and telescope both will decrease.
4. microscope will decrease but that of the telescope will increase.
Subtopic:  Simple & Compound Microscope |
 70%
From NCERT
AIPMT - 2014
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The angle of a prism is \(A\) One of its refracting surfaces is silvered. Light rays falling at an angle of incidence \(2{A}\) on the first surface return back through the same path after suffering reflection at the silvered surface. The refractive index \(\mu,\) of the prism, is:
1. \(2\text{sin}A\)
2. \(2\text{cos}A\)
3. \(\frac{1}{2}\text{cos}A\)
4. \(\text{tan}A\)

Subtopic:  Prisms |
 75%
From NCERT
AIPMT - 2014
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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. \(\frac{R}{2(\mu_1-\mu_2)}\)
2. \(\frac{R}{(\mu_1-\mu_2)}\)
3. \(\frac{2R}{(\mu_2-\mu_1)}\)
4. \(\frac{R}{2(\mu_1+\mu_2)}\)
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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The reddish appearance of the sun at sunrise and sunset is due to:
1. the scattering of light.
2. the polarisation of light.
3. the colour of the sun.
4. the colour of the sky.
Subtopic:  Total Internal Reflection |
 89%
From NCERT
NEET - 2013
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Two plane mirrors are inclined at \(70^\circ.\) A ray incident on one mirror at an angle, \(\theta\) after reflection falls on the second mirror and is reflected from there parallel to the first mirror. The value of \(\theta\) is:
1. \(45^\circ\)
2. \(30^\circ\)
3. \(55^\circ\)
4. \(50^\circ\)
Subtopic:  Reflection at Plane Surface |
 56%
From NCERT
NEET - 2013
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