1
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
With what speed should a galaxy move outward with respect to earth so that the sodium-D line at wavelength 5890 $$\mathop A\limits^o $$ is observed at 5896 $$\mathop A\limits^o $$ ?
A
306 km/sec
B
322 km/sec
C
296 km/sec
D
336 km/sec
2
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
The length of a metal wire is l1, when the tension in it is T1 and is l2 when the tension is T2. The natural length of the wire is :
A
$$\sqrt {{l_1}{l_2}} $$
B
$${{{l_1}{T_2} - {l_2}{T_1}} \over {{T_2} - {T_1}}}$$
C
$${{{l_1}{T_2} + {l_2}{T_1}} \over {{T_2} + {T_1}}}$$
D
$${{{l_1} + {l_2}} \over 2}$$
3
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
In an electromagnetic wave the electric field vector and magnetic field vector are given as $$\overrightarrow E = {E_0}\widehat i$$ and $$\overrightarrow B = {B_0}\widehat k$$ respectively. The direction of propagation of electromagnetic wave is along :
A
$$\left( {\widehat k} \right)$$
B
$$\widehat j$$
C
$$\left( { - \widehat k} \right)$$
D
$$\left( { - \widehat j} \right)$$
4
JEE Main 2021 (Online) 20th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
For a series LCR circuit with R = 100 $$\Omega$$, L = 0.5 mH and C = 0.1 pF connected across 220V$$-$$50 Hz AC supply, the phase angle between current and supplied voltage and the nature of the circuit is :
A
0$$^\circ$$, resistive circuit
B
$$ \approx $$ 90$$^\circ$$, predominantly inductive circuit
C
0$$^\circ$$, resonance circuit
D
$$ \approx $$ 90$$^\circ$$, predominantly capacitive circuit
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