A laser beam can be focussed on an area equal to the square of its wavelength A He-Ne laser radiates energy at the rate of 1mW and its wavelength is 632.8 nm. The intensity of focussed beam will be

\[1.5\times {{10}^{13}}\,W/{{m}^{2}}\]

\[2.5\times {{10}^{9}}\,W/{{m}^{2}}\]

A laser beam can be focussed on an area equal to the square of its wav

1.	A laser beam can be focussed on an area equal to the square of its wavelength A He-Ne laser radiates energy at the rate of 1mW and its wavelength is 632.8 nm. The intensity of focussed beam will be
A.	\[1.5\times {{10}^{13}}\,W/{{m}^{2}}\]
B.	\[2.5\times {{10}^{9}}\,W/{{m}^{2}}\]
C.	\[a\sin \theta =\lambda \]
D.	None of these
Answer» C. \[a\sin \theta =\lambda \]

Discussion

No Comment Found

Related MCQs

Radio wave diffract around building although light waves do not. The reason is that radio waves [AMU 2000]
A heavenly body is receding from earth such that the fractional change in l is 1, then its velocity is [DCE 2000]
The condition for observing Fraunhofer diffraction from a single slit is that the light wavefront incident on the slit should be [MP PMT 1987]
A parallel beam of monochromatic light of wavelength\[5000\,\,{AA}\]is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to [CBSE PMT 1993]
A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of incident beam. At the first maximum of the diffraction pattern the phase difference between the rays coming from the edges of the slit is [IIT?JEE 1995, 98]
Direction of the first secondary maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit) [KCET 1999]
If we observe the single slit Fraunhofer diffraction with wavelength l and slit width e, the width of the central maxima is 2q. On decreasing the slit width for the same l [UPSEAT 2004]
A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of the central bright fringe is [IIT-JEE 1994; KCET 2004]
When light is incident on a diffraction grating the zero order principal maximum will be [KCET 2004]
What will be the angular width of central maxima in Fraunhoffer diffraction when light of wavelength \[6000\,{AA}\] is used and slit width is \[12\times {{10}^{-5}}cm.\] [RPMT 2004]

A laser beam can be focussed on an area equal to the square of its wavelength A He-Ne laser radiates energy at the rate of 1mW and its wavelength is 632.8 nm. The intensity of focussed beam will be

Discussion

No Comment Found

Related MCQs

Reply to Comment