a ray of light travelling in air strikes a glass slab at an angle of 30 degree calculate the angle of?

refraction 9if refractive index of glass is 1.5?

Depends on where the angle of 30 degrees is measured from.

If it is 30 degrees to the normal then

n1*Sin(theta1) = n2*Sin(theta2)

1*Sin30 = 1.5Sin(theta2)

theta2 = 19.5 degrees

If however, it is 30 to the surface, then the angle with the normal is 60 degrees and

n1*Sin(theta1) = n2*Sin(theta2)

1*Sin60 = 1.5Sin(theta2)

theta2 = 35.3 degrees

Sini / Sinr = n2 / n1

so

sini x n1 / n2 = sinr

refractive index of air is 1.00
refractive index of glass is 1.5

sin 30 x 1.5 / 1.00 = 0.75

Inv sin 0.75 = 48.6 degrees

as the ray of light is travailing from glass to air it will refract away from the normal