From last week- Light

Last time Light is ? Particle Wave Both Neither

Last time Which color has the largest wave length? Red Which color has the shortest frequency? Which wave has the longest wavelength? Radio waves

Last time What is dispersion? Separation of visible light into different colors. Name the 3 properties of light? Light travels in straight lines Reflection- light reflects Refraction- light bends with a transparent medium.

Reflection and mirrors

Geometrical Optics In the study of how light behaves, it is useful to use “light rays” and the fact that light travels in straight lines. When light strikes the boundary between two media, three things may happen: reflection, refraction, or absorption. reflection refraction absorption Water Air

Reflection, Refraction, & Absorption Water Air reflection Reflection: A ray from air strikes the water and returns to the air. refraction absorption Refraction: A ray bends into the water toward the normal line. Absorption: A ray is absorbed atomically by the water and does not reappear.

The Laws of Reflection 1. The angle of inci- dence qi is equal to the angle of reflection qr : Water Air N reflection qr qi qi = qr All ray angles are measured with respect to normal N. 3. The rays are completely reversible. 2. The incident ray, the reflected ray, and the normal N all lie in the same plane.

reflection

The Plane Mirror A mirror is a highly polished surface that forms images by uniformly reflected light. Note: images appear to be equidistant behind mirror and are right-left reversed.

Definitions Object distance: The straight-line distance p from the surface of a mirror to the object. Image distance: The straight-line distance q from the surface of a mirror to the image. Object Image Object distance Image distance = p = q p q qi = qr

Real and Virtual Real images and objects are formed by actual rays of light. (Real images can be projected on a screen.) Real object Virtual image Light rays No light Virtual images and objects do not really exist, but only seem to be at a location. Virtual images are on the opposite side of the mirror from the incoming rays.

Image of a Point Object Plane mirror Real object p q = p q Virtual image Image appears to be at same distance behind mirror regardless of viewing angle.

Image of an Extended Object Plane mirror p q q = p Virtual image Image of bottom and top of guitar shows forward-back, right-left reversals.