•Young’s experiment ® wave
nature
•l = wavelength = length between crests/valleys
•n = frequency = number of crests passing per unit time
• = cycles per sec (Hz) =
1/P
•P = period = time for wave
to repeat itself
n nl = c (speed of light - celeritas) = 3 x 1010 cm/sec
n = 300, 000 km/s
nvisible light: 4000 < l > 8000 Ångstrom (1Å = 10-8 cm)
n
nFor a star, let B=
brightness = power/area = power/4pd2
•If L = total output of
star, L = Bx4pd2 and B = L/4pd2
•
n