reflection

Examples of reflection in the following topics:

• The Law of Reflection and Its Consequences

  • The law of reflection states that the angle of reflection equals the angle of incidence.
  • The law of reflection is very simple: The angle of reflection equals the angle of incidence.
  • When we see our reflection in a mirror , it appears that our image is actually behind the mirror -- we see the light coming from a direction determined by the law of reflection.
  • We expect to see reflections off a smooth surface.
  • The law of reflection states that the angle of reflection equals the angle of incidence: θr = θi.

• Polarization By Scattering and Reflecting

  • In the case of polarized sunglasses, for example, when you look through them, reflected light is not entirely filtered out; reflected light can be slightly polarized by the reflection process (as shown in ).
  • The reflected light is more horizontally polarized.
  • Since the light is split into two, and part of it is refracted, the amount of polarization to the reflected light depends on the index of refraction of the reflective surface.
  • where: θb = angle of reflection of complete polarization (also known as Brewster's angle); n1 = index of refraction of medium in which reflected light will travel; and n2 = index of refraction of medium by which light is reflected.
  • Calculate angle of reflection of complete polarization from indices of refraction

• Applications: Ultrasound, Sonar, and Medical Imaging

  • Sound waves reflect off different materials differently (when the reflections are collected, they can provide information and images).
  • Controlled reflection of such waves allows images to be received.
  • The use of ultrasound to create images is based on the reflection and transmission of a wave at a boundary.
  • The reflected rays are detected and used to construct an image of the object.
  • Ultrasound waves are sent out then reflected off the objects around the animal.

• Image Reflection by a Plane Mirror

  • A mirror is a reflective surface that bounces off light, thus producing a real or virtual image.
  • The object is the source of the incident rays, and the image is formed by the reflected rays.
  • An image formed by reflection may be real or virtual.
  • The way that we can predict how a reflection will look is by drawing a ray diagram.
  • The angle in which a light ray hits the mirror is the same angle in which it will be reflected back.

• Air Wedge

  • An incident beam of light encounters four boundaries at which the index of refraction of the media changes, causing four reflected beams (or Fresnel reflections) as shown in .
  • The first reflection occurs when the beam enters the first glass plate.
  • The second reflection occurs when the beam exits the first plate and enters the air wedge, and the third reflection occurs when the beam exits the air wedge and enters the second glass plate.
  • The fourth beam is reflected when it encounters the boundary of the second glass plate.
  • The air wedge angle, between the second and third Fresnel reflections, can be adjusted, causing the reflected light beams to constructively and destructively interfere and create a fringe pattern.

• Reflection and Transmission

  • Reflection and transmission often occur at the same time .
  • When the string is driven by an external force, partial reflection and transmission occurs as in Figure 18426.
  • For the incoming, reflected, and transmitted waves, we can try a solution of the following forms:
  • (This is why the '+' sign is chosen before $\omega t$ in the reflected wave.
  • We can define the transmission (t) and reflection (r) coefficients as

• The Ray Aspect of Light

  • Rays, or beams of light, can travel in three ways: directly, through a material, or indirectly (reflection).
  • When light is bounced off of a material, such as a mirror, this is called a reflection.
  • This is when a light ray, the incident ray, hits a reflective material and bounces off as the reflected ray at a specific angle.
  • This is called the angle of reflection .
  • This diagram shows how light rays reflects off of a surface.

• Total Polarization

  • When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized.
  • Thus, if the angle of reflection θ1 (angle of reflection) is equal to the alignment of the dipoles (90 - θ2), where θ2 is angle of refraction, no light is reflected.
  • When light hits a surface at a Brewster angle, reflected beam is linearly polarized. shows an example, where the reflected beam was nearly perfectly polarized and hence, blocked by a polarizer on the right picture.
  • In the picture at left, the polarizer is aligned with the polarization angle of the window reflection.
  • In the picture at right, the polarizer has been rotated 90° eliminating the heavily polarized reflected sunlight.

• Image Formation by Spherical Mirrors: Reflection and Sign Conventions

  • A mirror is a reflective surface that light does not pass through, but bounces off of and this produces an image.
  • The object is the source of the incident rays, and the image is formed by the reflected rays.
  • An image formed by reflection may be real or virtual.
  • Each incident ray is reflected according to the Law of Reflection.
  • The reflected rays diverge.

• Standing Waves on a String

  • Standing wave occurs due to the interference when transverse waves in strings are reflected and the incident and reflected waves meet.
  • It is then reflected from that end and starts to move back towards the original direction; at this point interference occurs. shows a transverse wave that is reflected from a fixed end.
  • When a transverse wave meets a fixed end, the wave is reflected, but inverted.
  • When either of the two scenarios of wave reflection occurs, the incident wave meets the reflected wave.
  • When a transverse wave meets a fixed end, the wave is reflected, but inverted.