1
JEE Main 2023 (Online) 31st January Morning Shift
Numerical
+4
-1

In a medium the speed of light wave decreases to $$0.2$$ times to its speed in free space The ratio of relative permittivity to the refractive index of the medium is $$x: 1$$. The value of $$x$$ is _________.

(Given speed of light in free space $$=3 \times 10^{8} \mathrm{~m} \mathrm{~s}^{-1}$$ and for the given medium $$\mu_{\mathrm{r}}=1$$)

2
JEE Main 2023 (Online) 30th January Morning Shift
Numerical
+4
-1

A point source of light is placed at the centre of curvature of a hemispherical surface. The source emits a power of $$24 \mathrm{~W}$$. The radius of curvature of hemisphere is $$10 \mathrm{~cm}$$ and the inner surface is completely reflecting. The force on the hemisphere due to the light falling on it is ____________ $$\times~10^{-8} \mathrm{~N}$$.

3
JEE Main 2022 (Online) 29th July Evening Shift
Numerical
+4
-1

Nearly 10% of the power of a $$110 \mathrm{~W}$$ light bulb is converted to visible radiation. The change in average intensities of visible radiation, at a distance of $$1 \mathrm{~m}$$ from the bulb to a distance of $$5 \mathrm{~m}$$ is $$a \times 10^{-2} \mathrm{~W} / \mathrm{m}^{2}$$. The value of 'a' will be _________.

4
JEE Main 2022 (Online) 29th June Evening Shift
Numerical
+4
-1

The displacement current of 4.425 $$\mu$$A is developed in the space between the plates of parallel plate capacitor when voltage is changing at a rate of 106 Vs$$-$$1. The area of each plate of the capacitor is 40 cm2. The distance between each plate of the capacitor is x $$\times$$ 10$$-$$3 m. The value of x is __________.

(Permittivity of free space, E0 = 8.85 $$\times$$ 10$$-$$12 C2 N$$-$$1 m$$-$$2).

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