1
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
In an experiment a convex lens of focal length 15 cm is placed coaxially on an optical bench in front of a convex mirror at a distance of 5 cm from it. It is found that an object and its image coincide, if the object is placed at a distance of 20 cm from the lens. The focal length of the convex mirror is :
A
27.5 cm
B
20.0 cm
C
25.0 cm
D
30.5 cm
2
JEE Main 2017 (Online) 9th April Morning Slot
+4
-1
A single slit of width 0.1 mm is illuminated by a parallel beam of light of wavelength 6000 $$\mathop A\limits^ \circ$$ and diffraction bands are observed on a screen 0.5 m from the slit. The distance of the third dark band from the central bright band is :
A
3 mm
B
9 mm
C
4.5 mm
D
1.5 mm
3
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
Let the refractive index of a denser medium with respect to a rarer medium be n12 and its critical angle be θC . At an angle of incidence A when light is travelling from denser medium to rarer medium, a part of the light is reflected and the rest is refracted and the angle between reflected and refracted rays is 90o. Angle A is given by :
A
$${1 \over {{{\cos }^{ - 1}}\left( {\sin {\theta _C}} \right)}}$$
B
$${1 \over {{{\tan }^{ - 1}}\left( {\sin {\theta _C}} \right)}}$$
C
$${\cos ^{ - 1}}\,\left( {\sin {\theta _C}} \right)$$
D
$${\tan ^{ - 1}}\,\left( {\sin {\theta _C}} \right)$$
4
JEE Main 2017 (Online) 8th April Morning Slot
+4
-1
A single slit of width b is illuminated by a coherent monochromatic light of wavelength $$\lambda$$. If the second and fourthminima in the diffraction pattern at a distance 1 m from the slit are at 3 cm and 6 cm respectively from the central maximum, what is the width of the central maximum ? (i.e. distance between first minimum on either side of the central maximum)
A
1.5 cm
B
3.0 cm
C
4.5 cm
D
6.0 cm
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