1
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The magnetic field associated with a light wave is given, at the origin, by B = B0 [sin(3.14 $$ \times $$ 107)ct + sin(6.28 $$ \times $$ 107)ct]. If this light falls on a silver plate having a work function of 4.7 eV, what will be the maximum kinetic energy of the photo electrons ?
(Take c = 3 $$ \times $$ 108 ms$$-$$1, h = 6.6 $$ \times $$ 10$$-$$34J-s)
A
6.82 eV
B
12.5 eV
C
8.52 eV
D
7.72 eV
2
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
In a car race on straight road, car A takes a time t less than car B at the finish and passes finishing point with a speed '$$\upsilon $$' more than that of car B. Both the cars start from rest and travel with constant acceleration a1 and a2 respectively. Then '$$\upsilon $$' is equal to :
A
$${{2{a_1}{a_2}} \over {{a_1} + {a_2}}}t$$
B
$$\sqrt {2{a_1}{a_2}} t$$
C
$$\sqrt {{a_1}{a_2}} t$$
D
$${{{a_1} + {a_2}} \over 2}t$$
3
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Charge is distributed within a sphere of radius R with a volume charge density $$\rho \left( r \right) = {A \over {{r^2}}}{e^{ - {{2r} \over s}}},$$ where A and a are constants. If Q is the total charge of this charge distribution, the radius R is :
A
a log $$\left( {1 - {Q \over {2\pi aA}}} \right)$$
B
$${a \over 2}$$ log $$\left( {{1 \over {1 - {Q \over {2\pi aA}}}}} \right)$$
C
a log $$\left( {{1 \over {1 - {Q \over {2\pi aA}}}}} \right)$$
D
$${a \over 2}$$ log $$\left( {1 - {Q \over {2\pi aA}}} \right)$$
4
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The pitch and the number of divisions, on the circular scale, for a given screw gauge are 0.5 mm and 100 respectively. When the screw gauge is fully tightened without any object, the zero of its circular scale lies 3 divisions below the mean line.

The readings of the main scale and the circular scale, for a thin sheet, are 5.5 mm and 48 respectively, the thickness of this sheet is :
A
5.755 mm
B
5.950 mm
C
5.725 mm
D
5.740 mm
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