The refracted light beam shown in Figure P35.8 forms an angle ɸ = 20.0º with the normal line NN 'in linseed oil. The refractive index of linseed oil is 1.48. Determine the angles (a) θ and (b) θ ’.

f is prop to m1xm2 double m1 double force

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west

365.25 earth days are in the year of a light year