1
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
Change Language
WB JEE 2021 Physics - Geometrical Optics Question 9 English
The cross-section of a reflecting surface is represented by the equation x2 + y2 = R2 as shown in the figure. A ray travelling in the positive x-direction is directed toward positive y-direction after reflection from the surface at point M. The coordinate of the point M on the reflecting surface is
A
$$\left( {{R \over {\sqrt 2 }},{R \over {\sqrt 2 }}} \right)$$
B
$$\left( { - {R \over 2}, - {R \over 2}} \right)$$
C
$$\left( { - {R \over {\sqrt 2 }},{R \over {\sqrt 2 }}} \right)$$
D
$$\left( {{R \over {\sqrt 2 }}, - {R \over {\sqrt 2 }}} \right)$$
2
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
For a plane electromagnetic wave, the electric field is given by

$$ \overrightarrow{E} = 90\sin (0.5 \times {10^3}x + 1.5 \times {10^{11}}t)\widehat k$$ V/m. The corresponding magnetic field B will be
A
$$\overrightarrow{B} = 3 \times {10^{ - 7}}\sin (0.5 \times {10^3}x + 1.5 \times {10^{11}}t)\widehat i$$ T
B
$$\overrightarrow{B} = 3 \times {10^{ - 7}}\sin (0.5 \times {10^3}x + 1.5 \times {10^{11}}t)\widehat j$$ T
C
$$\overrightarrow{B} = 27 \times {10^9}\sin (0.5 \times {10^3}x + 1.5 \times {10^{11}}t)\widehat j$$ T
D
$$\overrightarrow{B} = 3 \times {10^{ - 7}}\sin (0.5 \times {10^3}x + 1.5 \times {10^{11}}t)\widehat k$$ T
3
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Two metal wires of identical dimensions are connected in series. If $$\sigma$$1 and $$\sigma$$2 are the electrical conductivities of the metal wires respectively, the effective conductivity of the combination is
A
$$\sigma$$1 + $$\sigma$$2
B
$${{{\sigma _1}{\sigma _2}} \over {{\sigma _1} + {\sigma _2}}}$$
C
$${{2{\sigma _1}{\sigma _2}} \over {{\sigma _1} + {\sigma _2}}}$$
D
$${{{\sigma _1} + {\sigma _2}} \over {2{\sigma _1}{\sigma _2}}}$$
4
WB JEE 2021
MCQ (Single Correct Answer)
+2
-0.5
Change Language
A uniform rod of length L pivoted at one end P is freely rotated in a horizontal plane with an angular velocity $$\omega$$ about a vertical axis passing through P. If the temperature of the system is increased by $$\Delta$$T, angular velocity becomes $${\omega \over 2}$$. If coefficient of linear expansion of the rod is $$\alpha$$($$\alpha$$ << 1), then $$\Delta$$T will be
A
$${1 \over \alpha }$$
B
$${1 \over 2\alpha }$$
C
$${1 \over 4\alpha }$$
D
$$\alpha$$
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