M5 Phy 1stSem Final Flat mirror and Reflection

​Flat Mirrors

​Objectives

• Distinguish between specular and diffuse reflections of light.

• Apply the law of reflection to flat mirrors.

• Describe the nature of images formed by flat mirrors.

​Reflection is the change in direction of an electromagnetic wave at a surface that causes it to move away from the surface.

Light always travels in a straight line through a uniform substance, but its path changes when it encounters a different material.

Key Terms
​
Reflection is the change in direction of an electromagnetic wave at a surface that causes it to move away from the surface.
Angle of incidence is the angle between a ray that strikes a surface and the line perpendicular to that surface at the point of contact.
Angle of reflection is the angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves.
Ray diagrams help locate images formed by mirrors using simple geometry.

The texture of a surface influences how it reflects light. Rough surfaces like paper or cloth cause light to scatter in many directions, known as diffuse reflection.
In contrast, smooth, shiny surfaces like mirrors or water reflect light in a single direction, called specular reflection. A surface is considered smooth if its variations are small compared to the light's wavelength. In this context, "reflection" refers specifically to specular reflection.

​Let us answer together

​Which of the following are examples of specular reflection, and which are examples of diffuse reflection?

1. reflection of light from the surface of a lake on a calm day
2. reflection of light from a plastic trash bag
3. reflection of light from the lens of eyeglasses
4. reflection of light from a carpet

Multiple Choice

Which is an example of specular reflection?

• reflection of light from the surface of a lake on a calm day

• reflection of light from a plastic trash bag

Multiple Choice

What is an example of diffuse reflection?

• reflection of light from the surface of a lake on a calm day

• reflection of light from a plastic trash bag

Multiple Choice

What is an example of diffuse reflection?

• reflection of light from the lens of eyeglasses

• reflection of light from a carpet

Multiple Choice

What is an example of specular reflection?

• reflection of light from the lens of eyeglasses

• reflection of light from a carpet

Angle of incidence is the angle between a ray that strikes a surface and the line perpendicular to that surface at the point of contact.
Angle of reflection is the angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves.

​Incoming and reflected angles are equal. When light hits a smooth surface, the angle at which it strikes is equal to the angle at which it reflects.

A flat mirror reflects light from an object, such as a pencil, causing the light rays to spread out and appear to come from a point behind the mirror. This point is where the image is perceived to be, and the distance from the object to the mirror (p) is equal to the distance from the mirror to the image (q). Additionally, the image is the same size as the object.

​Virtual image is an image from which light rays appear to diverge, even though they are not actually focused there; a virtual image cannot be projected on a screen.

Ray tracing can be used to locate the image of any object placed in front of a flat mirror by focusing on a single point, such as the object's tip. Once this point is located, the rest of the image can be completed. The image in a flat mirror appears reversed, which can be observed by placing writing in front of the mirror and noticing how the letters are flipped. The angle of the word and its reflection relative to the mirror remains the same.

Summary
​
• Light obeys the law of reflection, which states that the incident and reflected angles of light are equal.
• Flat mirrors form virtual images that are the same distance from the mirror’s surface as the object is.

Color and Polarization

Objectives

• Recognize how additive colors affect the color of light.

• Recognize how pigments affect the color of reflected light.

• Explain how linearly polarized light is formed and detected.

Key Terms
​
​Polirization of light is the process of transforming unpolarized light waves to polarized light waves is called the polarization of light.

Linear polarization is the alignment of electromagnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other.

​The color of an object can appear different under various lighting because objects absorb some light wavelengths and reflect others. The perceived color depends on the wavelengths that are reflected.

​An object reflects all wavelengths of light, it appears the same color as the light illuminating it, similar to a white object under that light. A colored object, like a green leaf, absorbs all colors except its own, reflecting that color. If an object reflects no light, it appears black. Leaves appear green due to chlorophyll, which is destroyed in autumn, allowing other colors to be reflected.

Additive primary colors produce white light when combined.
White light can be created by combining elementary colors. This can be done by recombining dispersed light using a lens or by mixing light passed through red, green, and blue filters. These are known as additive primary colors, which can produce all colors of the spectrum when combined in different proportions.

Combining red light with green light creates yellow light. When two primary colors combine, they form a complementary color. For example, red and green produce yellow, and adding blue to yellow results in white light.

Subtractive primary colors filter out all light when combined. Mixing blue and yellow light produces white light, but combining blue and yellow pigments results in green. This difference occurs because pigments absorb (or subtract) certain light colors. Yellow pigment absorbs blue and violet, reflecting other colors like red and green. Blue pigment absorbs red and yellow, reflecting blue and green. When mixed, only green is reflected.

Pigments subtract colors from white light, and the result depends on what is not absorbed. The primary subtractive colors—cyan, magenta, and yellow—combine to produce red, green, or blue pigments. Mixed together, they create black by absorbing all colors.

Summary

• Light of different colors can be produced by adding light consisting of the primary additive colors (red, green, and blue).

• Pigments can be produced by combining subtractive colors (magenta, yellow, and cyan).

• Light can be linearly polarized by transmission, reflection, or scattering.

​Polarization of Light Waves

​Linear polarization is the alignment of electromagnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other.

Light typically consists of waves with electric fields oscillating in random directions, known as unpolarized light. By filtering these waves to allow only those with electric fields to oscillate in the same direction, a beam of linearly polarized light is produced.

​Polirization of light is the process of transforming unpolarized light waves to polarized light waves is called the polarization of light.

1. Light can be linearly polarized through transmission. When light reflects at a certain angle from a surface, it becomes completely polarized parallel to that surface. For horizontal surfaces, like water, the reflected light is horizontally polarized, causing glare. Polarizing sunglasses filter out this glare by having a vertical transmission axis that blocks the horizontally polarized light. Additionally, light can be polarized by scattering, where sunlight striking air molecules causes the emitted light to become polarized.

2.Light can be polarized by reflection and scattering. When light reflects at a certain angle from a surface, it becomes completely polarized parallel to that surface. For horizontal surfaces, like water, the reflected light is horizontally polarized, causing glare. Polarizing sunglasses filter out this glare by having a vertical transmission axis that blocks the horizontally polarized light. Additionally, light can be polarized by scattering, where sunlight striking air molecules causes the emitted light to become polarized.

Multiple Choice

________ is the change in direction of an electromagnetic wave at a surface that causes it to move away from the surface.

• Reflection

• Diffusion

• Diverge

• Refraction

Multiple Choice

_______ always travels in a straight line through a uniform substance, but its path changes when it encounters a different material.

• Reflection

• Diffusion

• Light

• Electromagnetic wave

Multiple Choice

Rough surfaces like paper or cloth cause light to scatter in many directions, this type of reflection is known as _______.

• specular reflection

• diffuse reflection

• Light

• Electromagnetic wave

Multiple Choice

Smooth and shiny surfaces like mirrors or water reflect light in a single direction and this type of reflection is called ___________.

• specular reflection

• diffuse reflection

• Light

• Electromagnetic wave

Multiple Choice

________ is the angle between a ray that strikes a surface and the line perpendicular to that surface at the point of contact.

• specular reflection

• diffuse reflection

• Angle of incidence

• Angle of reflection

Multiple Choice

_________ is the angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves.

• specular reflection

• diffuse reflection

• Angle of incidence

• Angle of reflection

Multiple Choice

​Incoming and reflected angles are not equal.

• True

• False

Multiple Choice

​Virtual image is an image from which light rays appear to diverge, even though they are not actually focused there; a virtual image cannot be projected on a screen. This virtual image is formed in a flat mirror.

• True

• False

Multiple Choice

_________ is the process of transforming unpolarized light waves to polarized light waves is called the polarization of light.

• specular reflection

• diffuse reflection

• Angle of incidence

• Angle of reflection

Multiple Choice

​The color of an object can appear different under various lighting because objects absorb some light frequencies and reflect others.

• True

• False

Multiple Choice

What are those colors that produce white light when combined.

• Additive primary colors

• Subtractive primary colors

• Pigments

• White

Multiple Select

What are the primary additive colors?

• Red

• Green

• Blue

• Yellow

Multiple Choice

Is it true that when two primary colors combine, do they form a complementary color?

• No

• Yes

Multiple Choice

Combining red light with green light creates _________.

• Yellow

• Blue

• Red

• Green

Multiple Choice

Combining red light with blue light creates _________.

• Yellow

• Magenta

• Red

• Green

Multiple Choice

Combining green light with blue light creates _________.

• Yellow

• Magenta

• Cyan

• Green

Multiple Choice

Adding blue to yellow results in _______.

• Yellow

• Blue

• Red

• White

Multiple Choice

What are those colors that filter out all light when combined.

• Additive primary colors

• Subtractive primary colors

• White

Multiple Select

What are the primary subtractive colors?

• cyan

• Green

• magenta

• Yellow

Multiple Choice

________ is the process of transforming unpolarized light waves into polarized light waves.

• Upolarization of light

• Polarization of light

• Reflection of light

Multiple Choice

_______ is the alignment of electromagnetic waves in such a way that the vibrations of the electric fields in each of the waves are parallel to each other.

• Upolarization of light

• Polarization of light

• Reflection of light

• ​Linear polarization

Multiple Select

Light can be linearly polarized by ___________.

• Upolarization of light

• Polarization of light

• reflection or scattering

• transmission

​1.________ is the change in direction of an electromagnetic wave at a surface that causes it to move away from the surface.
2._______ always travels in a straight line through a uniform substance, but its path changes when it encounters a different material.
3.Rough surfaces like paper or cloth cause light to scatter in many directions, this type of reflection is known as _______.
4._________ is the angle formed by the line perpendicular to a surface and the direction in which a reflected ray moves.
5. ________ image is formed in a flat mirror.
6, 7 and 8 ) What are the primary additive colors?
9-10 ) Light can be linearly polarized by _________ and ____________.

​Write your answers in your notebook.