1
NEET 2018
MCQ (Single Correct Answer)
+4
-1
In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength $$\lambda $$ of the light used is 5896 $$\mathop A\limits^0 $$ and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20o. To increase the fringe angular width to 0.21o (with same $$\lambda $$ and D) the separation between the slits needs to be changed to
A
1.9 mm
B
1.8 mm
C
2.1 mm
D
1.7 mm
2
NEET 2018
MCQ (Single Correct Answer)
+4
-1
Unpolarised light is incident from air on a plane surface of a material of refractive index $$\mu $$. At a particular angle of incidence i, it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?
A
Reflected light is polarised with its electric vector parallel to the plane of incidence
B
Reflected light is polarised with its electric vector perpendicular to the plane of incidence
C
$$i = {\sin ^{ - 1}}\left( {{1 \over \mu }} \right)$$
D
i = tan-1$$\left( {{1 \over \mu }} \right)$$
3
NEET 2018
MCQ (Single Correct Answer)
+4
-1
An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of
A
small focal length and large diameter
B
large focal length and small diameter
C
large focal length and large diameter
D
small focal length and small diameter
4
NEET 2018
MCQ (Single Correct Answer)
+4
-1
An electron of mass m with an initial velocity $$\overrightarrow v = {v_0}\widehat i$$ (v0 > 0) enters an electric field $$\overrightarrow E = - {\overrightarrow E _0}\widehat i$$ (E0 = constant > 0) at t = 0. If $$\lambda $$0 is its de-Broglie wavelength initially, then its de- Broglie wavelength at time t is
A
$${{{\lambda _0}} \over {\left( {1 + {{e{E_0}} \over {m{v_0}}}t} \right)}}$$
B
$${{\lambda _0}\left( {1 + {{e{E_0}} \over {m{v_0}}}t} \right)}$$
C
$$\lambda $$0t
D
$$\lambda $$0
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