1
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A progressive wave travelling along the positive x-direction is represented by y(x,t) = Asin(kx – $$\omega $$t + $$\phi $$). Its snapshot at t = 0 is given in the figure. JEE Main 2019 (Online) 12th April Morning Slot Physics - Waves Question 78 English
For this wave, the phase $$\phi $$ is :
A
$${\pi \over 2}$$
B
$$\pi $$
C
0
D
$$ - {\pi \over 2}$$
2
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
An excited He+ ion emits two photons in succession, with wavelengths 108.5 nm and 30.4 nm, in making a transition to ground state. The quantum number n, corresponding to its initial excited state is (for photon of wavelength $$\lambda $$, energy $$E = {{1240\,eV} \over {\lambda (in\,nm)}}$$) :
A
n = 4
B
n = 7
C
n = 5
D
n = 6
3
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
A submarine (A) travelling at 18 km/hr is being chased along the line of its velocity by another submarine (B) travelling at 27 km/hr. B sends a sonar signal of 500 Hz to detect A and receives a reflected sound of frequency $$\upsilon $$. The value of $$\upsilon $$ is close to: (Speed of sound in water =1500 ms–1)
A
507 Hz
B
502 Hz
C
499 Hz
D
504 Hz
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