Basic Science and Technology - Junior Secondary 3 - Light energy

TERM: 2^ND TERM

WEEK: 5

CLASS: Junior Secondary School 3

AGE: 14 years

DURATION: 40 minutes each for 2 periods

DATE:

SUBJECT: Basic Science

TOPIC: Light energy

SPECIFIC OBJECTIVES: At the end of the lesson, the learners should be able to

1. ) Define light
2. ) Explain the reflection of light and its types
3. ) Explain refraction of light and outline the consequences of refraction
4. ) Explain how an object is formed on the eye
5. ) Discuss dispersion of light and the concept of rainbow

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, story-telling, videos from source

INSTRUCTIONAL MATERIALS: Recommended Basic Science textbooks for Junior Secondary School 3

INSTRUCTIONAL PROCEDURES: PERIOD 1-2:

NOTE

LIGHT ENERGY
Light is a form of energy that travels in waves and is visible to the human eye. It is part of the electromagnetic spectrum and can travel through various mediums, including air, water, and space. Light enables us to see objects and is essential for processes like photosynthesis.

Reflection of Light:
Reflection is the bouncing back of light rays when they hit a smooth or shiny surface. Reflection enables us to see objects and forms the basis for how mirrors work. There are two main types of reflection:

• Specular Reflection: This occurs on smooth, shiny surfaces, such as mirrors, where light rays reflect in a single, organized direction, creating a clear image.
• Diffuse Reflection: This occurs on rough or uneven surfaces, where light rays scatter in multiple directions, leading to a scattered or blurry reflection with no clear image.

Refraction of Light and Its Consequences:
Refraction is the bending of light as it passes from one medium to another with a different density, such as from air to water. This change in speed causes light to change direction.

Consequences of Refraction

Refraction leads to several optical effects, including:

• Magnification: Lenses in glasses and cameras magnify objects due to the bending of light.
• Apparent Depth: Objects under water appear closer to the surface than they actually are.
• Formation of Lenses: Refraction is used in lenses, enabling vision correction, microscopes, and telescopes.

How an Object is Formed on the Eye:
Light rays from an object enter the eye through the cornea and pass through the aqueous humor, pupil, and lens. The lens focuses the light onto the retina, a light-sensitive layer at the back of the eye. The retina converts the light signals into electrical impulses, which are then transmitted to the brain through the optic nerve. The brain interprets these signals, allowing us to see the object in clear detail.

Dispersion of Light and the Concept of Rainbow:
Dispersion is the splitting of white light into its component colors (red, orange, yellow, green, blue, indigo, and violet) when it passes through a medium like a glass prism. Each color bends at a different angle due to variations in wavelength, creating a spectrum of colors.

Concept of Rainbow: A rainbow is a natural example of dispersion. When sunlight enters a raindrop, it refracts, disperses into its component colors, reflects off the inside of the raindrop, and refracts again as it exits. This series of refractions and reflections produces a colorful arc in the sky.

EVALUATION:

1. How does the reflection of light differ between specular and diffuse reflection, and how do these types of reflection affect our ability to see objects clearly?
2. What are some practical applications of refraction, and how does this phenomenon impact everyday objects like glasses and cameras?
3. Explain the process by which light enables the eye to form an image, and discuss the role of the retina in this process.
4. How does dispersion lead to the formation of a rainbow, and what role does refraction play in this natural phenomenon?
5. What are the consequences of refraction when viewing objects underwater, and how does this relate to the concept of apparent depth?

CLASSWORK: As in evaluation

CONCLUSION: The teacher marks their books and commends them positively