Two thin lenses when placed in contact, then the power of combination is +10D. If they are kept 0.25 m apart, then the power reduces to +6D. The focal lengths of the lenses (in m) will be
0.5 and 0.125
0.5 and 0.75
0.125 and 0.75
Both have same focal length i.e. 1.25
The focal length of the objective and eye lenses of a microscope are 1.6 cm and 2.5 cm respectively. The distance between the two lenses is 21. 7 cm. If the final image is formed at infinity, then the linear magnification is
11
110
1.1
44
A lens of focal length 1 m forms Fraunhofer diffraction pattern of a single slit of width 0.04 cm in its focal plane. The incident light contains two wavelengths λ1 and λ2 . It is found that the fourth minimum corresponding to λ1 and fifth minimum corresponding to λ2 occur at the same point 0.5 cm from central maximum, then λ1 and λ2 are
400 nm, 500 nm
500 nm, 700 nm
700 nm, 500 nm
500 nm, 400 nm
A thin prism placed in air produces minimum deviation of 4° in a light ray. If the prism 8 m is immersed in water, then the minimum deviation produced by it is
3°
5°
2°
1°
An astronomical telescope arranged for normal adjustment has a magnification of 6. Ifthe length ofthe telescope is 35cm, then the focal length of objective and eye piece respectively, are
30 cm, 5 cm
5 cm, 30 cm
40 cm, 5 cm
30 cm, 6 cm
The fossil bone has a 14C : 12C ratio which is (1 / 16) of that in a living animal bone. If the half-life time of 14C is 5730 years, thus the age of the fossil bone is
11460 years
17190 years
22920 years
45840 years
C.
22920 years
A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in figure. The current through the diode is
5 mA
10 mA
15 mA
20 mA
In the following circuit, the output Y becomes one for the inputs
A= 0, B = 1, C = 0
A = 1, B = 1, C = 0
A =1, B= 1, C = 1
A = 1, B= 0, C = 1
The energy levels of a certain atom are represented in the figure given below. During the transition from 2E to E level, a photon of wavelength is emitted. The wavelength of photon produced during transition from 4 / 3E level to E will be