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**Simulator****Previous Years AIEEE/JEE Mains Questions**Q. If a source of power $4 \mathrm{kW}$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called
(1) microwaves
(2) y-rays
(3) X-rays
(4) ultraviolet rays

**[AIEEEE 2010]**Ans. (3)
Power $=\frac{\text { nhc }}{\lambda} \lambda \approx 1 \mathrm{A} \equiv \mathrm{X}$ Rays

Q. An electromagnetic wave in vacuum has the electric and magnetic fields $\overrightarrow{\mathrm{E}}$ and $\overrightarrow{\mathrm{B}}$, which are
always perpendicular to each other. The direction of polarization is given by $\overrightarrow{\mathrm{X}}$ and that ofwave
propagation by $\overrightarrow{\mathrm{k}}$. Then
(1) $\overrightarrow{\mathrm{X}} \| \overrightarrow{\mathrm{B}}$ and $\overrightarrow{\mathrm{k}} \| \overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}$
(2) $\overrightarrow{\mathrm{X}} \| \overrightarrow{\mathrm{E}}$ and $\overrightarrow{\mathrm{k}} \| \overrightarrow{\mathrm{B}} \times \overrightarrow{\mathrm{E}}$
(3) $\overrightarrow{\mathrm{X}} \| \overrightarrow{\mathrm{B}}$ and $\overrightarrow{\mathrm{k}} \| \overrightarrow{\mathrm{B}} \times \overrightarrow{\mathrm{E}}$
(4) $\overrightarrow{\mathrm{X}} \| \overrightarrow{\mathrm{E}}$ and $\overrightarrow{\mathrm{k}} \| \overrightarrow{\mathrm{E}} \times \overrightarrow{\mathrm{B}}$

**AIEEE-2012**Ans. (4)

Q. Match List-I (Electromagnetic wave type) with List-II (Its association/application) and select the correct option from the choices given below the lists:

**[JEE- Mains 2014]**Ans. (2)

Q. During the propagation of electromagnetic waves in a medium:
(1) Electric energy density is equal to the magnetic energy density
(2) Both electric magnetic energy densities are zero
(3) Electric energy density is double of the magnetic energy density
(4) Electric energy density is half of the magnetic energy density.

**[JEE- Mains 2014]**Ans. (1)

Q. A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 $\mathrm{m}$ from the diode is :-
(1) $5.48 \mathrm{V} / \mathrm{m}$
(2) $7.75 \mathrm{V} / \mathrm{m}$
(3) $1.73 \mathrm{V} / \mathrm{m}$
(4) $2.45 \mathrm{V} / \mathrm{m}$

**[JEE- Mains 2015]**Ans. (4)
$\mathrm{I}_{\mathrm{av}}=\frac{1}{2} \varepsilon_{0} \mathrm{E}^{2} \mathrm{C}=\frac{\mathrm{P}}{4 \pi \mathrm{r}^{2}}$
$\mathrm{E}=\sqrt{\frac{2 \mathrm{P}}{4 \pi \mathrm{r}^{2} \varepsilon_{0} \mathrm{c}}}$
On putting value we get
$=2.45 \mathrm{v} / \mathrm{m} .$

Q. Arrange the following electromagnetic radiations per quantum in the order of increasing energy :-

**[JEE- Mains 2016]**Ans. (2)
Energy $=\frac{\mathrm{hc}}{\lambda}$
order of wavelength
$x$ ray, VIBGYOR, Radiowaves