# there is a special incident ray that reflects right back to itself   how would you aim this incident ray to achieve that effect ? what is the angle of incidence of this incident ray/

labrat256 | Certified Educator

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When light rays reflect, the angle of incidence (the angle from which the ray is different from the normal of the surface, or the imaginary line coming straight out of the surface) is equal to the angle of reflection (which is again, the difference between the normal and the reflected angle).

In order to have an incident ray rebound on itself, the incident ray needs to be parallel to the surface normal. At this point, the angle of incidence is zero. Thus, the angle of reflection is also zero.

To achieve this, you would need to aim the ray of light directly at the surface, along its normal. This means you need to point it directly at the object, without any angle.

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astrosonuthird | Student

Ha ha ha.

Rashmi did copy & paste from mine answer.

rashmi0133 | Student

When light rays reflect, the angle of incidence (the angle from which the ray is different from the normal of the surface, or the imaginary line coming straight out of the surface) is equal to the angle of reflection (which is again, the difference between the normal and the reflected angle).There are two ways that this could be achieved, one, you could point it toward it's normal, or second, use a retro reflector, which is a mirror that the apollo 13 members put on the moon to put a sign of human activity on the moon.  The only advantage the retro reflector has, is no matter what angle you point a source of light at it, it will still reflect it back in the same dirction and angle.

Conclusion

Incident Ray = The ray which hits or falls on an object or a material is initially known as Incident Ray.

Reflected Ray = The ray which gets reflected after hitting the object is know as Reflected Ray.

astrosonuthird | Student

Incident Ray = The ray which hits or falls on an object or a material is initially known as Incident Ray.

Reflected Ray = The ray which gets reflected after hitting the object is know as Reflected Ray.

st-2 | Student

There are two ways that this could be achieved, one, you could point it toward it's normal, or second, use a retro reflector, which is a mirror that the apollo 13 members put on the moon to put a sign of human activity on the moon.  The only advantage the retro reflector has, is no matter what angle you point a source of light at it, it will still reflect it back in the same dirction and angle.

astrosonuthird | Student

You will find more on www.physicsforchildren.com.