1
JEE Main 2021 (Online) 31st August Evening Shift
Numerical
+4
-1
In a Young's double slit experiment, the slits are separated by 0.3 mm and the screen is 1.5 m away from the plane of slits. Distance between fourth bright fringes on both sides of central bright is 2.4 cm. The frequency of light used is ______________ $$\times$$ 1014 Hz.
2
JEE Main 2021 (Online) 31st August Evening Shift
Numerical
+4
-1
Cross-section view of a prism is the equilateral triangle ABC in the figure. The minimum deviation is observed using this prism when the angle of incidence is equal to the prism angle. The time taken by light to travel from P (midpoint of BC) to A is ______________ $$\times$$ 10$$-$$10 s. (Given, speed of light in vacuum = 3 $$\times$$ 108 m/s and cos30$$^\circ$$ = $${{\sqrt 3 } \over 2}$$)

3
JEE Main 2021 (Online) 26th August Evening Shift
Numerical
+4
-1
A source of light is placed in front of a screen. Intensity of light on the screen is I. Two Polaroids P1 and P2 are so placed in between the source of light and screen that the intensity of light on screen is I/2. P2 should be rotated by an angle of (degrees) so that the intensity of light on the screen becomes $${{3I} \over 8}$$.
4
JEE Main 2021 (Online) 26th August Evening Shift
Numerical
+4
-1
An object is placed at a distance of 12 cm from a convex lens. A convex mirror of focal length 15 cm is placed on other side of lens at 8 cm as shown in the figure. Image of object coincides with the object.

When the convex mirror is removed, a real and inverted image is formed at a position. The distance of the image from the object will be .............. (cm)
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