diffraction and interference explanation concepts

two source interference pattern

-monochromatic light is directed through 2 slits

-bright bands are caused by light waves arriving at the screen in phase and interfering constructively, this occurs when the path difference of light form slits to the screen is a whole number of wavelengths (corresponds to antinodal lines)

-dark bands are caused by light waves arriving at the screen fully out of phase and interfering destructively, this occurs when the path difference of light from slits to screen is a half number of wavelengths (corresponds to nodal lines)

-this causes the pattern of dark and bright spots

change in slit separation

if the separation of the slits is increased then the bands move closer together, vice versa

change in L (distance from screen)

if the screen is moved closer to the slits then the bands move closer, vice versa

explaining white light

-the pattern is created by the light going through the slits in the diffraction grating, spreading out and interfering

-when the waves hit a screen when the path difference is equal to a whole number of wavelengths constructive interference occurs with peaks meeting peaks and troughs meeting troughs creating bright light

-when the path difference is 1/2, 3/2, 5/2, and so on times the wavelength that light destructively interferes creating no or dim light

-white light is made of a range of wavelengths

-the central line is white because this is directly in front of the diffraction grating and the path difference is zero, so all wavelengths constructively interfere making white light

-on either side is a coloured spectrum because each angle has a different path difference, so a different wavelength will constructively interfere producing a different colour

-the dark regions are where no visible wavelength constructively interferes