When light travels from air to water at an angle which of the following happens? a) the light slows down and it changes direction away from the perpendicular. b) the light slows down and it changes direction towards the perpendicular. c) the light speeds up and it changes direction away from the perpendicular. d) the light speeds up and it changes direction towards the perpendicular.

b) The light slows down and it changes direction towards the perpendicular.

Explanation:

Light travels at different speed in different mediums.

Refractive index is equal to velocity of the light 'c' in empty space divided by the velocity 'v' in the substance.

Or ,

n = c/v.

Light travels at a slower speed in water as compared to air because there are more number of interfering molecules in the path of the light in case of water as compared to liquid.

When a light travels from lower denser medium say water to higher denser medium say water, it bends towards the perpendicular as its speed reduces in that medium.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form