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Wave Optics

Question
CBSEENPH12039491

Monochromatic light is incident on a glass prism of angle A. If the refractive index of the material oft the prism is μ, a ray incident at an angle θ, on the face AB would get transmitted through the face AC of the prism provided

  • straight theta space greater than space sin to the power of negative 1 end exponent open square brackets straight mu space sin space open parentheses straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close parentheses close square brackets
  • straight theta space less than space sin to the power of negative 1 end exponent open square brackets straight mu space sin space open parentheses straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close parentheses close square brackets
  • straight theta less than cos to the power of negative 1 end exponent open square brackets straight mu space sin space open parentheses straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close parentheses close square brackets
  • straight theta space greater than cos to the power of negative 1 end exponent open square brackets straight mu space sin space open parentheses straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close parentheses close square brackets

Solution

A.

straight theta space greater than space sin to the power of negative 1 end exponent open square brackets straight mu space sin space open parentheses straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close parentheses close square brackets

The Ray will get transmitted through face AC if iAC < iC
Consider the ray diagram is shown below θ.

A ray of light incident on face AB at angle 
r1 = Angle of refraction on face AB
r2 = Angle of incidence at face AC
For transmission of light through face AC
iAC < iC or A-ri < iC
 or Sin (A-r1)1)< 1/μ
straight A minus straight r subscript 1 space less than space sin to the power of negative 1 end exponent space open parentheses 1 over straight mu close parentheses
sin space straight r subscript 1 space greater than space sin space open square brackets straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close square brackets
Now, applying snell's law at the face AB
1 x sin θ = μ sin r1 or sinr1 = sinθ/μ
fraction numerator sin space straight theta over denominator straight mu end fraction space greater than space sin space open square brackets straight A minus sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close square brackets
straight theta greater than space sin to the power of negative 1 end exponent open square brackets straight mu space sin space open curly brackets straight A space minus space sin to the power of negative 1 end exponent open parentheses 1 over straight mu close parentheses close curly brackets close square brackets

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