A plano convex lens fits exactly into a plano concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices $$\mu $$1 and $$\mu $$2 and R is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is
A, B and C are three points in a uniform electric field. The electric potential is
A
maximum at C
B
same at all the three points A, B and C
C
maximum at A
D
maximum at B
3
NEET 2013
MCQ (Single Correct Answer)
+4
-1
In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths $${\lambda _1}$$ = 12000 $$\mathop A\limits^ \circ $$ and $${\lambda _2}$$ = 10000 $$\mathop A\limits^ \circ $$. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?
A
4 mm
B
3 m
C
8 mm
D
6 mm
4
NEET 2013
MCQ (Single Correct Answer)
+4
-1
A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?
A
The angular width of the central maximum will decrease.
B
The angular wifth of the central maximum will be unaffected.
C
Diffraction pattern is not observed on the screen in the case of electrons.
D
The angular width of the central maximum of the diffraction pattern will increase.