physics
posted by orange .
1) If the first order maximum of HeNe light exits a diffraction grating at an angle of 40.7o, at what angle will the first order maximum of violet light with a wavelength of 418 nm exit?
What is HeNe light?????
2) The most efficient antennae have a size of half the wavelength of the radiation they are emitting. How long should an antenna be to broadcast at 980 kHz?

HeNe light is a gas laser in which He is excited, and those ions then collide with Neon to release energy. Of the most common spectrums of this laser, 633 nm is the most common wavelength.
d sinTheta=m lambda
d = 633*E9/sin40.7
so, the question: d sinGamma=m lambda
633E9/sin40.7 * sinGamma=418E9
solve for The angle Gamma.
b. 980khz*wavelenth= speed light
solve fodr wavelength, then the size of the antenna is half that. 
HeNe laser operates at a wavelength of 632.8 nm in the red part of the visible spectrum
d•sinφ = k•λ,
for HeNe:
d•sin40.7º =1•632.8•10^9….(1)
For violet light:
d•sinφ=1•418•10^9 ……(2)
Divide(1) by (2)
d•sin40.7º/ d•sin φ =632.8•10^9/418•10^9,
sinφ = sin40.7º •418/632.8 = 0.433.
φ =arcsin 0.433 =25.68º.
λ = c/f = 3•10^8/980000 =305.9 m
L = λ/2 =153 m.
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