1
JEE Main 2024 (Online) 1st February Evening Shift
+4
-1
Monochromatic light of frequency $6 \times 10^{14} \mathrm{~Hz}$ is produced by a laser. The power emitted is $2 \times 10^{-3} \mathrm{~W}$.

How many photons per second on an average, are emitted by the source ?

(Given $\mathrm{h}=6.63 \times 10^{-34} \mathrm{Js}$ )
A
$5 \times 10^{15}$
B
$7 \times 10^{16}$
C
$6 \times 10^{15}$
D
$9 \times 10^{18}$
2
JEE Main 2024 (Online) 1st February Evening Shift
+4
-1
Conductivity of a photodiode starts changing only if the wavelength of incident light is less than $660 \mathrm{~nm}$. The band gap of photodiode is found to be $\left(\frac{\mathrm{X}}{8}\right) \mathrm{eV}$. The value of $\mathrm{X}$ is :

(Given, $\mathrm{h}=6.6 \times 10^{-34} \mathrm{Js}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ )
A
11
B
13
C
15
D
21
3
JEE Main 2024 (Online) 1st February Morning Shift
+4
-1
The de Broglie wavelengths of a proton and an $\alpha$ particle are $\lambda$ and $2 \lambda$ respectively. The ratio of the velocities of proton and $\alpha$ particle will be :
A
$8: 1$
B
$1: 2$
C
$1: 8$
D
$4: 1$
4
JEE Main 2024 (Online) 31st January Evening Shift
+4
-1

In a photoelectric effect experiment a light of frequency 1.5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

A
doubled
B
halved
C
Zero
D
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