Light of wavelength `lamda` from a small 0.5 mW He-Ne laser source, used in the school laboratory, shines from a spacecraft of mass 1000 kg. Estimate the time needed for the spacecraft to reach a velocity of `1.0km^(-1)` from rest. The momentum p of a photon of wavelength `lamda` is given by `p=(h)/(lamda)`, where h is Planck's constant.

There are two very small natural particle which are held fixed at a separation of 1 m from each other . Using some mechanism , one electron is transferred from particle to the other and electric potential energy lost in this process is converted into a photon of wavelength lamda_1 . When one more electron is transferred in the same direction , the wavelength of photon emitted is lamda_2 . If lamda_1 -lamda_2=5^pxx23^q calculate the value of pq. {:(0,1,2,3,4,5,6,7,8,9):}

Two parallel beams of light P and Q (separation d) containing radiation of wavelengths 4000A and 5000A (which are mutually coherent in each wavelength separately) are incident normally on a prism as shown in fig. The refractive index of the prism as a function of wavelength is given by the relation. mu(lamda)=1.20+(b)/(lamda^(2)) Where lamda is in A and b is positive constant. The value of b is such that the condition wave length and is not satisfied for the other. (a) Find the value of b. (b) find the deviation of the beams transmitted through the face AC. (c) A convergent lens is used to bring these transmitted beams into focus. If the intensities of transmission form the face AC, are 41 and I respectively, find the resultant intensity at the focus.

A laser light of wavelength 660 nm is used to weld Retina detachment. If a laser pulse of width 60 ms and power 0.5 kW is used, the approximate number of photons in the pulse are (Take Planck's Constant, h=6.62xx10^(-34)Js )

A laser light of wavelength 660 nm is used to weld Retina detachment. If a laser pulse of width 60 ms and power 0.5 kW is used, the approximate number of photons in the pulse are (Take Planck's Constant, h=6.62xx10^(-34)Js )