# physics

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(1) If an electromagnetic wave has a period of 4.8 μs, what is the frequency and wavelength?

I know how to find the frequency but for the wavelength how can we find it without the velocity being given????

(2) The beam of a helium-neon laser (λ = 632.8 nm) is incident on a slit of width 0.085 mm. A screen is placed 95.0 cm away from the slit. How far from the central band is the first dark band? If the slit was two times wider, would the first dark band be closer or farther form the central band?

• physics -

1. Since is is an electromagnetic wave, the velocity is c = 3.0*10^8 m/s

2. Use the single slit diffraction equation.

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/sinslit.html

The first dark band is at an angular distance ë/d from the central bright band. Doubling the slit width decreases the band separation distance by half.

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