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Reflection and Mirrors - Detailed Help

Assignment RM1: The Law of Reflection

Objectives:

The student should be able to identify and apply the definitions of the angle of incidence, the angle of reflection, incident ray and reflected ray.

The student should be able to apply the law of reflection in order to identify the angle of incidence and reflection if given other angle information.

Reading:

The Physics Classroom, Reflection and Mirrors Unit, Lesson 1, Part c

	The angle of incidence is defined as the angle between the ____ and the ____.
	Definition of Angle of Incidence: The angle of incidence is the angle made by the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface.
	A common mistake made by beginning physics students is to believe that the angle of incidence is the angle between the incident ray and the mirror surface. But don't be fooled! Angles of incidence (and reflection) are always measured between the ray of light and the normal line.
	What is the definition of the angle of incidence?

	The angle of reflection is defined as the angle between the ____ and the ____.
	Definition of Angle of Reflection: The angle of reflection is the angle made by the ray of light leaving a surface (reflected ray) and the normal line drawn to the surface at the location where the ray leaves from the surface.
	A common mistake made by beginning physics students is to believe that the angle of reflection is the angle between the reflected ray and the mirror surface. But don't be fooled! Angles of reflection (and incidence) are always measured between the ray of light and the normal line.
	What is the definition of the angle of reflection?

	The diagram below depicts a ray of light reflecting off a planar surface. The angle of incidence is depicted by angle _____.
	Definition of Angle of Incidence: The angle of incidence is the angle made by the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface.
	A common mistake made by beginning physics students is to believe that the angle of incidence is the angle between the incident ray and the mirror surface. But don't be fooled! Angles of incidence (and reflection) are always measured between the ray of light and the normal line.
	What is the definition of the angle of incidence?

	The diagram below depicts a ray of light reflecting off a planar surface. The angle of reflection is depicted by angle _____.
	Definition of Angle of Reflection: The angle of reflection is the angle made by the ray of light leaving a surface (reflected ray) and the normal line drawn to the surface at the location where the ray leaves from the surface.
	A common mistake made by beginning physics students is to believe that the angle of reflection is the angle between the reflected ray and the mirror surface. But don't be fooled! Angles of reflection (and incidence) are always measured between the ray of light and the normal line.
	What is the definition of the angle of reflection?

	The diagram below depicts light reflecting off a planar surface. The incident ray, reflected ray, normal and surface are labeled with a letter. The incident ray is labeled with a letter ____, the reflected ray is labeled with a letter ____, and the normal with a letter _____. (Enter the three letters in order with no spaces or commas between letters.)
	The diagram shows a mirror surface (denoted by the horizontal line with the yellow backing), two rays of light which have arrowheads to denote the direction of travel, and a normal line. It is common convention to represent light rays by straight lines which have arrowheads at one end.
	Definition of Incident Ray: An incident ray is a ray of light which is approaching a mirror surface. Definition of Reflected Ray: A reflected ray is a ray of light which is leaving from (or has reflected off of) a mirror surface. Definition of Normal Line: A normal line is a line drawn perpendicular to a mirror surface at the location where a ray of light strikes the surface.
	What is an incident ray? What is a reflected ray? What is a normal line?

	The diagram below depicts light reflecting off a planar surface. The incident and reflected rays are labeled. If ray A makes an angle of 25 degrees with the surface, then the angle of reflection is _____ degrees.
	The Law of Reflection: When a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. The incident ray and reflected ray are always located within the same plane.
	Definition of Angle of Incidence: The angle of incidence is the angle made by the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface. Definition of Angle of Reflection: The angle of reflection is the angle made by the ray of light leaving a surface (reflected ray) and the normal line drawn to the surface at the location where the ray leaves from the surface.
	A common mistake made by beginning physics students is to believe that the angle of incidence is the angle between the incident ray and the mirror surface. But don't be fooled! Angles of incidence (and reflection) are always measured between the ray of light and the normal line. If the angle between the incident ray and the mirror surface is 25 degrees, the angle of incidence is NOT 25 degrees. However, it can be determined using a quick math trick. See Math Magic section below.
	The normal line makes a 90 degree angle with the mirror surface. The incident ray divides this 90 degree angle into two smaller angles - the angle of incidence and the angle between the mirror surface and the incident ray. The sum of these angle measures is equal to 90 degrees.
	What is the definition of the angle of incidence? What is the relationship between the angle measurements for an incoming light ray and an outgoing light ray?

	The diagram below depicts light reflecting off a planar surface. If angle A is a 25 degree angle, then the angle of reflection is ____ degrees.
	The Law of Reflection: When a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. The incident ray and reflected ray are always located within the same plane.
	Definition of Angle of Incidence: The angle of incidence is the angle made by the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface. Definition of Angle of Reflection: The angle of reflection is the angle made by the ray of light leaving a surface (reflected ray) and the normal line drawn to the surface at the location where the ray leaves from the surface.
	A common mistake made by beginning physics students is to believe that the angle of incidence is the angle between the incident ray and the mirror surface. But don't be fooled! Angles of incidence (and reflection) are always measured between the ray of light and the normal line. If the angle between the incident ray and the mirror surface is 25 degrees, the angle of incidence is NOT 25 degrees. However, it can be determined using a quick math trick. See Math Magic section below.
	The normal line makes a 90 degree angle with the mirror surface. The incident ray divides this 90 degree angle into two smaller angles - the angle of incidence and the angle between the mirror surface and the incident ray. The sum of these angle measures is equal to 90 degrees.
	What is the definition of the angle of incidence? What is the relationship between the angle measurements for an incoming light ray and an outgoing light ray?

	The diagram below depicts light reflecting off a planar surface. If angle A is a 25 degree angle, then the angle of reflection is ____ degrees.
	The Law of Reflection: When a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. The incident ray and reflected ray are always located within the same plane.
	Definition of Angle of Incidence: The angle of incidence is the angle made by the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface. Definition of Angle of Reflection: The angle of reflection is the angle made by the ray of light leaving a surface (reflected ray) and the normal line drawn to the surface at the location where the ray leaves from the surface.
	What is the definition of the angle of incidence? What is the relationship between the angle measurements for an incoming light ray and an outgoing light ray?

	The diagram below depicts a ray of light (drawn in red) approaching a planar surface. Which one of the green rays is representative of the reflected ray?
	The diagram shows a mirror surface (denoted by the black diagonal line with the yellow backing), an incident ray (denoted by the red line with the arrowhead), and five possible reflected rays (denoted by the green lines with the arrowheads). If is common convention to represent light rays by straight lines which have arrowheads at one end to indicate the direction of travel.
	The Law of Reflection: When a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection. The incident ray and reflected ray are always located within the same plane.
	With the incident ray and the mirror surface drawn, you should be able to determine the angle of incidence. Either eyeball a quick estimate or position a transparent protractor on the screen and measure it. The angle of reflection should be equal to the angle of incidence (see Physics Rules section above). Only one of the five green rays has an angle of incidence equal to the angle of reflection. You can use the protractor (or a simple estimate) to determine which ray it is.
	What is the definition of the angle of incidence? What is the relationship between the angle measurements for an incoming light ray and an outgoing light ray?