REFLECTION OF LIGHT Quantum Physics Chapter 2mrkarensworld.weebly.com/uploads/3/8/6/4/38645049/02_reflection_of...REFLECTION OF LIGHT Quantum Physics ... Convex mirrors can only form

REFLECTION OF LIGHT

Quantum Physics – Chapter 2

Reflection refers to the change in the direction of light after it meets a surface that returns it to its original medium.

Alexander Karen 2014 2

Specular (regular) reflection occurs if the wavelength of the light is longer than the size of the irregularities on the surface.

This means that if parallel light rays are directed at the surface, the reflected rays will consist of parallel rays as well.


Specular (regular) reflection occurs on smooth surfaces.

EX: mirrors, calm bodies of water, polished metals.


Diffuse (irregular) reflection occurs if the size of the irregularities is greater than or approximately equal to the light’s wavelength.

This means that the rays are reflected in a disorderly manner and in different directions.


Diffuse (irregular) reflection occurs on rough, matte and dull surfaces give rise to diffuse reflection.

EX: brick walls, asphalt, wood furniture, sheets of paper.



QUANTUM PHYSICS - Pg. 43 # 5, 6


The incident ray is the light ray that travels toward the reflective surface.


The normal is an imaginary line that is perpendicular to the reflective surface and originates at the intersection of the incident ray and the reflective surface.


The angle of incidence (θi) is the angle formed by the incident ray and the normal.


The reflected ray is the light ray that travels away from the reflective surface.


The angle of reflection (θr) is the angle formed by the reflected ray and the normal.


The First Law of Reflection states that the incident ray, the reflected ray & the normal are all located in the same plane.


The Second Law of Reflection states that the angle of incidence is equal to the angle of reflection: θi = θr.



QUANTUM PHYSICS - Pg. 47 # 1-7


An image is a representation of an illuminated object produced by a series of points caused by the convergence of light rays originating from various points of an object or from the extension of these rays.

Images are characterized according to type, orientation, size & position.


An image can be real or virtual.

An image is real if the optical system directs the light rays originating from a source point by converging them toward an image point. A real image can be projected onto a screen.

An image is virtual if its image points appear to originate from a fictitious extension of light rays. A virtual image cannot be projected onto a screen.


An image can be upright or inverted.

The image is upright if it is oriented in the same direction as the object.

The image is inverted if it is rotated by 180˚ with respect to the object.


The image can be smaller or larger than the object depending on the object’s position in relation to the optical system.

Magnification (M) is the ratio between the image height (hi) and the object height (ho.)


Images formed by a camera obscura are

Real

Inverted

Usually smaller than the object


In a camera obscura, the image height (hi) is inversely proportional to the distance between the illuminated object and the pinhole (do), but is indirectly proportional to the depth of the camera obscura (di.)


Images formed by plane mirrors are

Virtual

Upright

Same size as the object

Located behind the mirror at the same distance from the mirror as that of the object



When two plane mirrors are used, several images are formed. The number of images formed (N) depends on the angle (θ) between the two mirrors and can be determined by:




CONVEX vs CONCAVE MIRRORS

Spherical mirrors consist of a spherical cap cut from a reflective hollow sphere.


If the domed, exterior face of a spherical cap is used as a reflective surface, the mirror is convex.


If the hollow, interior face of a spherical cap is used as a reflective surface, the mirror is concave.



In a convex mirror, the centre (C) of the sphere is located on the opposite side of the reflective surface.


In a concave mirror, the centre (C) of the sphere is located on the side of the reflective surface.


The surface of a convex mirror causes light rays that are parallel to its principal axis to diverge.

For this reason convex mirrors are also called diverging mirrors.



V

The basic ray diagram for a convex mirror introduces a number of important terms:

Principal axis (P) - the line through the centre of curvature and the surface of the mirror.

Focal point (F) – the point at which the light rays that are parallel to the prinicipal axis (P) converge.

Focal length (f) – the distance between the vertex (V) and the focal point (F) or equal to half the radius of curvature: f = R/2


The basic ray diagram for a convex mirror introduces a number of important terms:

Centre of curvature (C) - the point at the centre of the sphere from which the spherical mirror originates.

Vertex (V) – the geometric centre of the mirror’s surface (also called a pole).

Radius of curvature (R) – the radius of the sphere or the distance between the centre of curvature (C) and the vertex (V)


However, for convex mirrors, their principal rays DO NOT pass through the principal points because these points are located behind the mirror.

In diagrams, it is customary to use dotted lines to extend the reflected rays behind the convex mirror.


R


Ray diagrams are constructed by taking the path of three distinct rays from a point on the object:

X) a ray parallel to the principal axis reflected through F (the principal focus)

Y) a ray passing through C which is then reflected back along its original path

Z) a ray passing through F, which is then reflected parallel to the principal axis

note - the convex mirror is considered to be so thin as to be represented by a vertical line





The surface of a concave mirror converges the light rays that are parallel to its principal axis toward a point located inside its curvature and referred to as the focal point (F).

For this reason concave mirrors are also called converging mirrors.



The basic ray diagram for a concave mirror introduces a number of important terms:

Principal axis (P) - the line through the centre of curvature and the surface of the mirror.

Focal point (F) – the point at which the light rays that are parallel to the prinicipal axis (P) converge.

Focal length (f) – the distance between the vertex (V) and the focal point (F) or equal to half the radius of curvature: f = R/2


The basic ray diagram for a concave mirror introduces a number of important terms:

Centre of curvature (C) - the point at the centre of the sphere from which the spherical mirror originates.

Vertex (V) – the geometric centre of the mirror’s surface (also called a pole).

Radius of curvature (R) – the radius of the sphere or the distance between the centre of curvature (C) and the vertex (V)


R


Sample Problem: A converging mirror reflects the light emitted by a distant object, focusing it at a point 34 cm from the mirror. What is the radius of curvature (R) of the mirror?

f = 34cm

R = ?

f = R / 2

R = 2f = 2(34cm) = 68cm

The radius of curvature (R) of the converging mirror is 68 cm.


Ray diagrams are constructed by taking the path of three distinct rays from a point on the object:

X) a ray parallel to the principal axis reflected through F (the principal focus)

Y) a ray passing through C which is then reflected back along its original path

Z) a ray passing through F, which is then reflected parallel to the principal axis

note - the concave mirror is considered to be so thin as to be represented by a vertical line



Spherical aberration is an optical defect that occurs when the rays that are parallel to the principal axis (P) AND that strike a concave spherical mirror at large angles of incidence (θi) are not focused at one common focal point (F.)


http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=TvmKTu7j8Yza2M&tbnid=tdltRXApFiO_lM:&ved=0CAcQjRw&url=http://www.schoolphysics.co.uk/age16-19/Optics/Reflection/text/Spherical_mirror_defects/index.html&ei=RBswVMDGGo2XyASZ6oDIDg&bvm=bv.76802529,d.aWw&psig=AFQjCNG5BGYZyFZHvYT-uX3Ku276-hJ6tw&ust=1412525072537274

To avoid spherical aberration, a parabolic mirror can be used to focus all incident rays at a single focal point.


http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=jiQ_xw94GiyltM&tbnid=Pyztzg8LR3-blM:&ved=0CAcQjRw&url=http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/basics/g12/&ei=MhwwVOq2JNCmyASNjoG4AQ&bvm=bv.76802529,d.aWw&psig=AFQjCNGXW0wBVEiqLkleOZJs86lOBTxZmQ&ust=1412525439044623

http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=jiQ_xw94GiyltM&tbnid=Pyztzg8LR3-blM:&ved=0CAcQjRw&url=http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/basics/g12/&ei=MhwwVOq2JNCmyASNjoG4AQ&bvm=bv.76802529,d.aWw&psig=AFQjCNGXW0wBVEiqLkleOZJs86lOBTxZmQ&ust=1412525439044623

QUANTUM PHYSICS - Pg. 54 # 1, 3, 4, 6, 7


Convex mirrors can only form one kind of image – these images are always

virtual

upright

Smaller

located behind the mirror

(Closer to the mirror that the object was.)


Trial 6: All convex mirrors form a virtual image reduced in size. VIRTUAL. UPRIGHT. SMALLER.


Concave mirrors can form five different kind of images – depending on the object placement in regards to the mirror.


Trial 1: The object is located beyond the center of curvature. The image is located between the center of curvature (C) and the principal focus (F). REAL. INVERTED. SMALLER.


Trial 2: The object is located at the center of curvature. The image is located at the center of curvature. REAL. INVERTED. SAME SIZE.


Trial 3: The object is located between the center of curvature and the principal focus. The image is located beyond the center of curvature. REAL. INVERTED. LARGER.


Trial 4: The object is located at the principal focus. NO IMAGE IS FORMED. All rays are reflected from the mirror as parallel rays.


Trial 5: The object is located between the principal focus and the mirror. The image appears to be located behind the mirror. VIRTUAL. UPRIGHT. LARGER.




A 4.00-cm tall light bulb is placed a distance of 45.7 cm from a concave mirror having a focal length of 15.2 cm. Determine the image distance and the image size.


F = 15.2 cm hi = ho = 4 cm di = do = 45.7 cm

1 = 1 - 1 di 15.2 45.7 di = 22.8 cm

hi = [(4cm)(22.8cm)] (45.7cm) hi = 1.99 cm


Image Height (hi)

http://www.google.ca/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=hN_gZ-MS4RlnsM&tbnid=U--VzcSPvsu9ZM:&ved=0CAcQjRw&url=http://www.tutorvista.com/content/science/science-ii/reflection-light/sign-convention-mirrors.php&ei=8TQwVL31M5eryASWp4C4Dg&bvm=bv.76802529,d.aWw&psig=AFQjCNGcxKtjwjh0x0JHfaQR9AbQyNKhiw&ust=1412531553324314



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REFLECTION OF LIGHT Quantum Physics Chapter 2mrkarensworld.weebly.com/uploads/3/8/6/4/38645049/02_reflection_of...REFLECTION OF LIGHT Quantum Physics ... Convex mirrors can only form