1
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
2
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
$$\lambda \,\infty \,{1 \over {{{\left( {v - {v_0}} \right)}^{{1 \over 2}}}}}$$
3
JEE Main 2019 (Online) 11th January Morning Slot
+4
-1
Heat treatment of muscular pain involves radiation of wavelength of about 900 nm. Which spectral line of H atom is suitable for this purpose?

[RH = 1 $$\times$$ 105 cm–1, h = 6.6 $$\times$$ 10–34 Js, c = 3 $$\times$$ 108 ms–1]
A
Balmer, $$\infty$$ $$\to$$ 2
B
Paschen, 5 $$\to$$ 3
C
Paschen, $$\infty$$ $$\to$$ 3
D
Lyman, $$\infty$$ $$\to$$ 1
4
JEE Main 2019 (Online) 10th January Evening Slot
+4
-1
The ground state energy of hydrogen atom is – 13.6 eV. The energy of second excited state of He+ ion in eV is :
A
$$-$$ 6.04
B
$$-$$ 54.4
C
$$-$$ 27.2
D
$$-$$ 3.4
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