Page 09 13. A ray of monochromatic light is incident on a grating as shown. monochromatic light grating central maximum first order maximum first order maximum 36° The wavelength of the light is 633 nm. The separation of the slits on the grating is A 1·96 × 10−7 m B 1·08 × 10−6 m C 2·05 × 10−6 m D 2·15 × 10−6 m E 4·10 × 10−6 m. 14. Light travels from glass into air. Which row in the table shows what happens to the speed, frequency and wavelength of the light as it travels from glass into air? Speed Frequency Wavelength A decreases stays constant decreases B decreases increases stays constant C stays constant increases increases D increases increases stays constant E increases stays constant increases 15. The irradiance of light from a point source is 32 W m−2 at a distance of 4·0 m from the source. The irradiance of the light at a distance of 16 m from the source is A 0·125 W m−2 B 0·50 W m−2 C 2·0 W m−2 D 8·0 W m−2 E 128 W m−2. [Turn over