A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called______________?
(A) center of curvature
(B) focus
(C) optical center
(D) aperture
Dioptre power of an concave lens of 10 cm focal length is_______________?
(A) 10 dioptre
(B) 10 dioptre
(C) 1 / 10 dioptre
(D) 1 / 10 dioptre
The minimum distance between an object and its real image in a convex lens is_____________?
(A) 2 f
(B) 2.5 f
(C) 3f
(D) 4f
A convex lens gives a virtual image only when the objects lies_________________?
(A) between principal focus and center of curvature
(B) beyond 2 f
(C) at the principal focus
(D) between principal focus and optical center
Image of an object 5 mm high is only 1 cm high. Magnification produced by lens is__________________?
(A) 0.5
(B) 0.2
(C) 1
(D) 2
X-ray are________________?
(A) of unknown nature
(B) high energy electrons
(C) high energy photons
(D) radio isotopes
Hydrogen atom does not emit X-rays because _________________?
(A) its energy levels are too close to each other
(B) its energy levels are too far apart
(C) it is too small in size
(D) it has a single electron
Excited atoms return to their ground state in_______________?
(A) 10-10s
(B) 10-8s
(C) 10-6s
(D) 10-9s
In hydrogen spectrum which one of the following series lies in the ultraviolet region ?
(A) Balmer series
(B) Pfund series
(C) Bracket series
(D) Lymann series