1
JEE Main 2017 (Online) 9th April Morning Slot
MCQ (Single Correct Answer)
+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
MCQ (Single Correct Answer)
+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)
MCQ (Single Correct Answer)
+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)
MCQ (Single Correct Answer)
+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
$${{{\lambda _A}} \over {{\lambda _B}}} = {1 \over 2}$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination
JEE MainJEE AdvancedWB JEE
Graduate Aptitude Test in Engineering
GATE CSEGATE ECEGATE EEGATE MEGATE CEGATE PIGATE IN
Medical
NEET