Finding the Angle of Incidence in a Plane Mirror: Reflection of Light Homework

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SUMMARY

The discussion focuses on calculating the angle of incidence for light reflecting off a plane mirror to reach a person's eyes. The person stands 3.6 meters from the mirror with their eyes 1.8 meters above the floor. The angle of incidence equals the angle of reflection, and using trigonometry, the angle can be determined by calculating the inverse tangent of the height difference (0.9 meters) divided by the distance to the mirror (3.6 meters). The solution involves drawing a diagram to visualize the problem effectively.

PREREQUISITES
  • Understanding of basic optics principles, specifically the law of reflection.
  • Knowledge of trigonometric functions, particularly tangent and inverse tangent.
  • Ability to interpret and create geometric diagrams for problem-solving.
  • Familiarity with the concept of angles in relation to a normal line in optics.
NEXT STEPS
  • Learn how to apply the law of reflection in different optical scenarios.
  • Study trigonometric identities and their applications in real-world problems.
  • Practice drawing and analyzing geometric diagrams in optics.
  • Explore advanced optics concepts, such as refraction and total internal reflection.
USEFUL FOR

Students studying physics, particularly those focusing on optics, as well as educators looking for effective methods to teach reflection and trigonometry in practical applications.

TheHamburgler1
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Homework Statement



A person stands 3.6m in front of a wall that is covered floor to ceiling with a plane mirror. His eyes are 1.8m above the floor. He holds a flashlight between his feet and manages to point it at the mirror. At what angel of incidence must the light strike the mirror so the light will reach his eyes?


Homework Equations


angle of incidence=angle of reflection


The Attempt at a Solution



I don't know what equation to use to get the answer
 
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Try drawing a picture of the problem. Diagrams are your best friend in optics problems.
 
link2001 said:
Try drawing a picture of the problem. Diagrams are your best friend in optics problems.
Excellent advice, link2001!

Think trigonometry.
 
yep, use trigonomety, draw a triangle, put x as the angle to the normal, the normal length is infinite but draw it as 3.6, and the height from the feet of the person , so that makes theta= inverse of tan( 0.9 divided by 3.6), that should give the angle to the normal. :D
 

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