1
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
$${{{a_1} + {a_2}} \over 2}t$$
2
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
A musician using an open flute of length 50 cm producess second harmonic sound waves. A person runs towards the musician from another end of hall at a speed of 10 km/h. If the wave speed is 330 m/s, the frequency heard by the running person shall be close to :
A
666 Hz
B
753 Hz
C
500 Hz
D
333 Hz
3
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
4
JEE Main 2019 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
In a communication system operating at wavelength 800 nm, only one percent of source frequency is available as signal bandwith. The number of channels accomodated for transmitting TV signals of band width 6 MHz are (Take velocity of light c = 3 $$ \times $$ 108m/s, h = 6.6 $$ \times $$ 10$$-$$34 J-s)
A
3.75 $$ \times $$ 106
B
3.86 $$ \times $$ 106
C
6.25 $$ \times $$ 105
D
4.87 $$ \times $$ 105
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