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1
JEE Main 2021 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
In the Young's double slit experiment, the distance between the slits varies in time as
d(t) = d0 + a0 sin$$\omega$$t; where d0, $$\omega$$ and a0 are constants. The difference between the largest fringe width and the smallest fringe width obtained over time is given as :
A
$${{2\lambda D({d_0})} \over {(d_0^2 - a_0^2)}}$$
B
$${{2\lambda D{a_0}} \over {(d_0^2 - a_0^2)}}$$
C
$${{\lambda D} \over {d_0^2}}{a_0}$$
D
$${{\lambda D} \over {{d_0} + {a_0}}}$$
2
JEE Main 2021 (Online) 22th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
A ray of light passes from a denser medium to a rarer medium at an angle of incidence i. The reflected and refracted rays make an angle of 90$$^\circ$$ with each other. The angle of reflection and refraction are respectively r and r'. The critical angle is given by

A
sin$$-$$1 (tan r)
B
sin$$-$$1 (cot r)
C
sin$$-$$1 (tan r')
D
tan$$-$$1 (sin i)
3
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
With what speed should a galaxy move outward with respect to earth so that the sodium-D line at wavelength 5890 $$\mathop A\limits^o$$ is observed at 5896 $$\mathop A\limits^o$$ ?
A
306 km/sec
B
322 km/sec
C
296 km/sec
D
336 km/sec
4
JEE Main 2021 (Online) 20th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Region I and II are separated by a spherical surface of radius 25 cm. An object is kept in region I at a distance of 40 cm from the surface. The distance of the image from the surface is :

A
55.44 cm
B
18.23 cm
C
9.52 cm
D
37.58 cm
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