1
JEE Main 2024 (Online) 29th January Evening Shift
+4
-1

Two sources of light emit with a power of $$200 \mathrm{~W}$$. The ratio of number of photons of visible light emitted by each source having wavelengths $$300 \mathrm{~nm}$$ and $$500 \mathrm{~nm}$$ respectively, will be :

A
$$5: 3$$
B
$$3: 5$$
C
$$1: 5$$
D
$$1: 3$$
2
JEE Main 2024 (Online) 29th January Morning Shift
+4
-1

The de-Broglie wavelength of an electron is the same as that of a photon. If velocity of electron is $$25 \%$$ of the velocity of light, then the ratio of K.E. of electron and K.E. of photon will be:

A
$$\frac{1}{4}$$
B
$$\frac{8}{1}$$
C
$$\frac{1}{8}$$
D
$$\frac{1}{1}$$
3
JEE Main 2024 (Online) 27th January Evening Shift
+4
-1

The threshold frequency of a metal with work function $$6.63 \mathrm{~eV}$$ is :

A
$$16 \times 10^{15} \mathrm{~Hz}$$
B
$$16 \times 10^{12} \mathrm{~Hz}$$
C
$$1.6 \times 10^{15} \mathrm{~Hz}$$
D
$$1.6 \times 10^{12} \mathrm{~Hz}$$
4
JEE Main 2023 (Online) 15th April Morning Shift
+4
-1
The de Broglie wavelength of an electron having kinetic energy $\mathrm{E}$ is $\lambda$. If the kinetic energy of electron becomes $\frac{E}{4}$, then its de-Broglie wavelength will be :
A
$\sqrt{2} \lambda$
B
$2 \lambda$
C
$\frac{\lambda}{2}$
D
$\frac{\lambda}{\sqrt{2}}$
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