dispersion EK #936 p. 100 (EK 1001 physics)

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.

dudewheresmymd

Slowly Drifting...
10+ Year Member
Joined
Mar 17, 2010
Messages
838
Reaction score
264
EK no 936 (1000 questions physics) states "light will bend away from normal when entering air and toward the normal when exiting air. The blue light (higher frequency) will bend more at each interface...but then they show the blue light on top of the red light, shouldn't blue/violet light bend more towards the normal when entering glass from air and then away from normal when entering air from glass? I get that blue light has a higher n because of chromatic dispersion, but this question answer shows the exact opposite of what it should be? just wanted to make sure i'm not going crazy. thanks!
 
I drew a picture.

When the light refracts it does bend more but it bends towards the normal! The angle is measured from the normal so, higher index of refraction = lower angle of refraction. (By the way normal refers to the alignment of the object)
 

Attachments

  • 20140204_015714.jpg
    20140204_015714.jpg
    21.7 KB · Views: 80
I drew a picture.

When the light refracts it does bend more but it bends towards the normal! The angle is measured from the normal so, higher index of refraction = lower angle of refraction. (By the way normal refers to the alignment of the object)

Right so let's take blue, it has a lower wavelength, lower velocity, higher n, just as a normal light ray would enter water from air and bend towards the normal, blue should bend towards the normal at the first (AIR to glass interface) EVEN MORE SO than red, and then at the second glass--> air interface, all types of light n2 is going down so theta exit (glass to air) should be greater away therefore blue light should be dispersed the most and opposite from what they have right?
 
I'm having a hard time understanding your question.. Are you asking why entering makes blue bend more towards the normal and then bends away while exiting?
 
I'm having a hard time understanding your question.. Are you asking why entering makes blue bend more towards the normal and then bends away while exiting?

hmm take a look at TBR book II p.244 (answer choice B in EK 1001) is what TBR has in their description of dispersion...however, the correct answer says it's C (in EK 1001 which is not the same as TBR's prism of dispersion where it has blue coming out at bottom away from red at top and the angle of incidences are the same as in answer choice B in the EK book as well as TBR's description of dispersion)...isn't answer choice C contradictory to TBR then or are they both acceptable?
 
Yes both are correct but C is more correct because EK asks you to display chromatic dispersion. This is when light bends around the object, changing it's path. Essentially it wanted the picture the light in the prism longer (more chromatic dispersion).
 
Top