1
JEE Main 2019 (Online) 12th January Morning Slot
+4
-1
A particle A of mass 'm' and charge 'q' is accelerated by a potential difference of 50 V. Another particle B of mass ' 4 m' and charge 'q' is accelerated by a potential difference of 2500 V. The ratio of de-Broglie wavelengths $${{{\lambda _A}} \over {{\lambda _B}}}$$ is close to :
A
4.47
B
10.00
C
14.14
D
0.07
2
JEE Main 2019 (Online) 11th January Evening Slot
+4
-1
In a photoelectric experiment, the wavelength of the light incident on a metal is changed from 300 nm to 400 nm. The decrease in the stopping potential is close to: ($${{{hc} \over e}}$$ = 1240 nm$$-$$V)
A
0.5 V
B
1.0 V
C
2.0 V
D
1.5 V
3
JEE Main 2019 (Online) 11th January Morning Slot
+4
-1
If the de Broglie wavelength of an electron is equal to the 10–3 times the wavelength of a photon of frequency 6 $$\times$$ 1014 Hz, then the speed of electron is equal to : (Speed of light = 3 $$\times$$ 108 m/s, Planck's constant = 6.63 $$\times$$ 10–34 J.s, Mass of electron = 9.1 $$\times$$ 10–31 kg)
A
1.7 $$\times$$ 106 m/s
B
1.45 $$\times$$ 106 m/s
C
1.1 $$\times$$ 106 m/s
D
1.8 $$\times$$ 106 m/s
4
JEE Main 2019 (Online) 10th January Evening Slot
+4
-1
A metal plate of area 1 $$\times$$ 10–4 m2 is illuminated by a radiation of intensity 16 mW/m2. The work function of the metal is 5 eV. The energy of the incident photons is 10 eV and only 10% of it produces photo electrons. The number of emitted photoelectrons per second and their maximum energy, respectively, will be
A
1014 and 10 eV
B
1012 and 5 eV
C
1011 and 5 eV
D
1010 and 5 eV
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