1
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
A convex lens 'A' of focal length 20 cm and a concave lens 'B' of focal length 5 cm are kept along the same axis with a distance 'd' between them. If a parallel beam of light falling on 'A' leaves 'B' as a parallel beam, then the distance 'd' in cm will be :
A
30
B
25
C
15
D
50
2
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
The escape velocity from the Earth's surface is v. The escape velocity from the surface of another planet having a radius, four times that of Earth and same mass density is :
A
4$$\upsilon $$
B
$$\upsilon $$
C
2$$\upsilon $$
D
3$$\upsilon $$
3
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
An electromagnetic wave of wavelength '$$\lambda$$' is incident on a photosensitive surface of negligible work function. If 'm' mass is of photoelectron emitted from the surface has de-Broglie wavelength $$\lambda$$d, then :
A
$$\lambda = \left( {{{2h} \over {mc}}} \right){\lambda _d}^2$$
B
$$\lambda = \left( {{{2m} \over {hc}}} \right){\lambda _d}^2$$
C
$${\lambda _d} = \left( {{{2mc} \over h}} \right){\lambda ^2}$$
D
$$\lambda = \left( {{{2mc} \over h}} \right){\lambda _d}^2$$
4
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since :
A
a large aperture contributes to the quality and visibility of the images.
B
a large area of the objective ensures better light gathering power.
C
a large aperture provides a better resolution.
D
All the above.
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