1
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
A Laser light of wavelength 660 nm is used to weld Retina detachment. If a Laser pulse of width 60 ms and power 0.5 kW is used the approximate number of photons in the pulse are :

[Take Planck's constant h $$=$$ 6.62 $$\times$$ 10$$-$$34 Js]
A
1020
B
1018
C
1022
D
1019
2
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
The maximum velocity of the photoelectrons emitted from the surface is v when light of frequency n falls on a metal surface. If the incident frequency is increased to 3n, the maximum velocity of the ejected photoelectrons will be :
A
less than $$\sqrt 3$$ v
B
v
C
more than $$\sqrt 3 \,v$$
D
equal to $$\sqrt 3 \,v$$
3
JEE Main 2017 (Offline)
+4
-1
An electron beam is accelerated by a potential difference V to hit a metallic target to produce X–rays. It produces continuous as well as characteristic X-rays. If $$\lambda$$min is the smallest possible wavelength of X-ray in the spectrum, the variation of log$$\lambda$$min with log V is correctly represented in:
A
B
C
D
4
JEE Main 2017 (Offline)
+4
-1
A particle A of mass m and initial velocity v collides with a particle B of mass m/2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths $${\lambda _A}$$ to $${\lambda _B}$$ after the collision is:
A
$${{{\lambda _A}} \over {{\lambda _B}}} = {1 \over 3}$$
B
$${{{\lambda _A}} \over {{\lambda _B}}} = 2$$
C
$${{{\lambda _A}} \over {{\lambda _B}}} = {2 \over 3}$$
D
$${{{\lambda _A}} \over {{\lambda _B}}} = {1 \over 2}$$
EXAM MAP
Medical
NEET