1.

Calculate the kinetic energy of a moving electron which has a wavelength of 4.8 pm. [mass of electron = 9.11 xx 10^(-31) kg, h = 6.626xx 10^(-34) Kg m^2s^(-1) ].

Answer»

Solution :According to d-broglie equation
`lamda = (h)/(mv) `
`v = (h)/(m lamda)`
` therefore v = (h)/(m lamda) = (6.626 xx 10^(-34) kg m^2 s^(-1) )/(9.11 xx 10^(-31) kg xx 4.8 xx 10^(-12) m) = 1.516 xx 10^8 ms^(-1)`
KINETIC energy` =1/2 mv^2 = 1/2 xx 9.11 xx 10^(-31) kg xx (1.516 xx 10^8 ms^(-1) )^2`
` = 10.47 xx 10^(-15) kg m^2 s^(-1)= 1.047 xx 10^(-14) J`


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