1.

An electromagneticwavetravellingin theX- directionhasfreqencyof2 xx 10^(14)Hzand electricfieldforthiswave?

Answer»

`VECB( x,t)= ( 3 xx 10^(-8)T ) SIN[ 2PI( 1.5 xx 10^(-6) x -2xx 10 ^4t)]`
` vecB( x, t)=( 9 xx 10 ^(-8)Thatk sin[ 2 pi( 1.5 xx 10^(-6 ) x-2xx 10^4t )]`
` vecB( x, t) = ( 9 xx 10^(-8)T )hati sin[ 2 pi( 1.5 xx 10^(-6) x - 2 xx 10^4t)]`
`vecE (X,t)= ( 9 xx 10^(-8)T ) hatjsin [ ( 1.5 xx 10^(-6)x -2 xx 10^4 t)]`

SOLUTION :Therelationbetweenthe amplitudesof theelectricfieldand themagneticisgivenby
` B_0= (E_0 )/(c ) `
thus ,`B_0=(27)/( 3xx 10^8 ) = 9 xx 10^(-8) T `
the angularfrequency is givenby
`omega = 2pi f = 2 pi xx 2xx 10^(14)Hz `
Thedirectionof oscillationof the magneticfieldcan beeitheralongY - axisor z- axis
thusthe possiblechoiceshouldbe
` vecB(x,t)= ( 9xx 10 ^(-8)T ) hatk sin `
` [ 2 pi( 1.5 xx 10^(-6) x-2 xx 10^(14) t)]`
HEncethe correctoptionis (b)


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