Refraction n Why do swimming pools look less

Refraction n Why do swimming pools look less deep than they actually are? n Is the sun exactly where we see it in the sky? n Why is the sky blue? n Why are sunsets red/orange? Physics. SFC 10/14/2010

Refraction n In order to answer these questions we must first learn something about refraction. Incident Ray Refracted Ray Physics. SFC Refraction is the bending of light as it passes from one transparent material to another, e. g. from air to glass. § When light travels from a rarer medium (air) into a denser medium (glass) it bends towards the normal When light travels from a denser medium (glass) into rarer medium (air) it bends away from the normal Normal Air Glass n § 10/14/2010

Refraction § This helps to explain why swimming pools appear less deep than they actually are The eye traces the light rays back in a straight line. Where these rays meet is where the bottom of the pool appears to be Eye Apparent Depth Where the tile appears to be Tile at bottom of pool Physics. SFC 10/14/2010

Refraction n When light passes from water into air it refracts quite a bit due to the relatively large difference in density between water and air. n The smaller the difference in density between the two media the less the light refracts n When light passes from free space (vacuum) into air it refracts by a small amount. However, this still has a noticeable effect. Physics. SFC 10/14/2010

Refraction n When light passes from the sun into our atmosphere it bends by a small amount. The eye traces the light rays back in a straight line. This is where the sun appears to be. Physics. SFC For this reason the sun appears ‘higher’ in the sky than it actually is. This ensures that our days are a little longer than they would otherwise be. 10/14/2010

Refraction n n When white light passes through a prism or a diffraction grating it splits up into the seven colours of the rainbow. This phenomenon is called dispersion. Dispersion occurs in a prism due to refraction. Dispersion occurs in a diffraction grating due to diffraction and interference. To answer the final two questions lets look at dispersion in a prism. Physics. SFC 10/14/2010

Refraction Dispersion occurs in a prism due to refraction. This happens as the different colours in white light refract by different amounts. Red Orange Yellow Green Blue White light Indigo Prism Physics. SFC Violet Blue/violet refract the most whereas red/orange refract the least. 10/14/2010

Refraction We now know: n why swimming pools look less deep than they actually are. n that the sun is not exactly where we see it in the sky. But ………………. n why is the sky blue? n why are sunsets red/orange? Physics. SFC 10/14/2010