1
JEE Main 2019 (Online) 12th January Evening Slot
+4
-1
If the de Broglie wavelength of the electron in nth Bohr orbit in a hydrogenic atom is equal to 1.5 $$\pi$$a0 (a0 is Bohr radius), then the value of n/z is -
A
0.75
B
0.40
C
1.50
D
1.0
2
JEE Main 2019 (Online) 12th January Evening Slot
+4
-1
The upper stratosphere consisting of the ozone layer protects us from sun's radiation that falls in the wavelength region of -
A
200-315 nm
B
400-550 nm
C
0.8-1.5 nm
D
600-750 nm
3
JEE Main 2019 (Online) 12th January Morning Slot
+4
-1
What is the work function of the metal if the light of wavelength 4000$$\mathop A\limits^ \circ$$ generates photoelectrons of velocity 6 $$\times$$ 105 ms–1 from it ?
(Mass of electron = 9 $$\times$$ 10–31 kg;
Velocity of light = 3 $$\times$$ 108 ms$$-$$1
Plank's constant = 6.626 $$\times$$ 10–34 Js;
Charge of electron = 1.6 $$\times$$10–19 JeV–1)
A
4.0 eV
B
0.9 eV
C
2.1 eV
D
3.1 eV
4
JEE Main 2019 (Online) 11th January Evening Slot
+4
-1
The de Broglie wavelength ($$\lambda$$) associated with a photoelectron varies with the frequency (v) of the incident radiation as, [v0 is threshold frequency] :
A
$$\lambda \,\infty \,{1 \over {{{\left( {v - {v_0}} \right)}^{{3 \over 2}}}}}$$
B
$$\lambda \,\infty \,{1 \over {{{\left( {v - {v_0}} \right)}^{{1 \over 4}}}}}$$
C
$$\lambda \,\infty \,{1 \over {\left( {v - {v_0}} \right)}}$$
D
$$\lambda \,\infty \,{1 \over {{{\left( {v - {v_0}} \right)}^{{1 \over 2}}}}}$$
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