As you may have learned when studying the properties of thermal energy, building

Question

As you may have learned when studying the properties of thermal energy, building contractors often install double-glazed windows to prevent therma energy ("heat") from entering/exiting the building. Although effective as insulators, such windows present interesting optical effects. In the figure, a double-glazed window comprises two identical panes of glass (n_g = 1.54) separated by an air gap. If the light encounters the glass at an angle of 40.00' with respect to the glass, find the shift in path deltax as the light enters the room. (Use n_a = 1.00)

Explanation / Answer

The light gets reflected in the glass interface

Sini/Sinr= ng/na

Sin40/sinr=1.54/1

r= 24.67deg

As the emegent ray incident on the second glass is parallel to the first initial incident ray, it would again undergo similar shift as the ray emerging from the first slap.

Lateral shift of the ray emerging from the first glass is given by:

Shift= t/cosr×sin(i-r)

= 42/cos(24.67)×sin(40-24.67)

=12.22mm

Delta(x)= 2(12.22)

=24.44mm

  (65)

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