1
COMEDK 2022
MCQ (Single Correct Answer)
+1
-0

Speed of electromagnetic wave in a medium having relative permittivity $$\varepsilon_r$$ and relative permeability $$\mu_r$$ is (speed of light in air, $$c=3\times10^8$$ m/s)

A
$${1 \over {\sqrt {{\mu _r}{\varepsilon _r}} }}$$
B
$${c \over {\sqrt {{\mu _r}{\varepsilon _r}} }}$$
C
$$c\sqrt {{{{\mu _r}} \over {{\varepsilon _r}}}} $$
D
$${c \over {{\mu _r}{\varepsilon _r}}}$$
2
COMEDK 2022
MCQ (Single Correct Answer)
+1
-0

The wavelength of the second line of Balmer series is 486.4 nm. What is the wavelength of the first line of Lyman series?

A
78.8 nm
B
121.6 nm
C
418.2 nm
D
610.5 nm
3
COMEDK 2022
MCQ (Single Correct Answer)
+1
-0

A bat emitting an ultrasonic wave of frequency 4.5 $$\times$$ 104 Hz at speed of 6 m/s between two parallel walls. The two frequencies heard by the bat will be

A
4.67 $$\times$$ 104 Hz, 4.34 $$\times$$ 104 Hz
B
4.34 $$\times$$ 104 Hz, 4.67 $$\times$$ 104 Hz
C
4.5 $$\times$$ 104 Hz, 5.4 $$\times$$ 104 Hz
D
4.67 $$\times$$ 103 Hz, 4.34 $$\times$$ 103 Hz
4
COMEDK 2022
MCQ (Single Correct Answer)
+1
-0

A disc of moment of inertia 4 kg - m$$^2$$ revolving with 16 rad/s is placed on another disc of moment of inertia 8 kg - m$$^2$$ revolving 4 rad/s. The angular frequency of composite disc

A
4 rad/s
B
$$\frac{3}{16}$$ rad/s
C
8 rad/s
D
$$\frac{16}{3}$$ rad/s
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