1
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.
2
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
Two charged spherical conductors of radius R1 and R2 are connected by a wire. Then the ratio of surface charge densities of the spheres ($$\sigma$$1 / $$\sigma$$2) is :
A
$${{R_1^2} \over {R_2^2}}$$
B
$${{R_1^{}} \over {R_2^{}}}$$
C
$${{R_2^{}} \over {R_1^{}}}$$
D
$$\sqrt {\left( {{{{R_1}} \over {{R_2}}}} \right)} $$
3
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
For a plane electromagnetic wave propagating in x-direction, which one of the following combination gives the correct possible directions for electric field (E) and magnetic field (B) respectively?
A
$$ - \widehat j + \widehat k, - \widehat j + \widehat k$$
B
$$ \widehat j + \widehat k, \widehat j + \widehat k$$
C
$$ - \widehat j + \widehat k, - \widehat j - \widehat k$$
D
$$\widehat j + \widehat k, - \widehat j - \widehat k$$
4
NEET 2021
MCQ (Single Correct Answer)
+4
-1
Change Language
A cup of coffee cools from 90$$^\circ$$C to 80$$^\circ$$C in t minutes, when the room temperature is 20$$^\circ$$C. The time taken by a similar cup of coffee to cool from 80$$^\circ$$C to 60$$^\circ$$C at a room temperature same at 20$$^\circ$$C is :
A
$${5 \over {13}}$$t
B
$${13 \over {10}}$$t
C
$${13 \over {5}}$$t
D
$${10 \over {13}}$$t
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