Students’ Learning Outcomes
· Differentiate between “Luminous and Non – Luminous” Objects.
· Identify and differentiate between transparent, opaque and translucent objects in their surroundings.
Information for Teachers
· Light is a form of energy which enables us to see the things around.
· The objects which emit light of their own are called luminous objects.
· The sun, a glowing bulb, a lighted candle and a glow warm are luminous objects.
· The things which don’t emit light of their own are called non-luminous objects.
· Non-Luminous objects can only be seen when light falling on them reflects back and enters into our eyes.
· A book, a chair and human body are examples of non-luminous objects.
· Some objects like Moon look luminous but actually they are not. They look bright because they reflect light falling on them.
· The things through which you can see across are called transparent, i. e. window glass thin plastic sheet etc. light can pass completely through transparent objects.
|Thin Plastic Jar|
|Transparent Pet Bottle|
· The non-transparent objects are called opaque. Light can’t pass through them i. e. wood, a wall, clayware, metals etc. are called opaque objects.
· The materials through which light can pass partially are called translucent, Example of translucent objects are given below.
Material / Resources
Candle, match box, book, wooden piece, shoe box, torch, tissue papers, piece of hard card board, a clear wrapping paper, mirror, white ball, textbook.
Worm up Activity
· Do the worm up activity to involve the students.
· Ask students: can you read a book in a dark room?
· If their answer is ‘no’ then, ask them again: How can you read the book?
· Write their responses on the board: by opening a window in day time. By switching on a bulb or by lighting a candle in light etc.
· Draw conclusion:
(A) Without light we can’t see the things around.
(B) Objects that give off light of their own are known as luminous objects.
· Ask a student to light up a torch and throw its light on the mirror. Ask the students:
—Does the mirror glow with its own light? (Expected response: It doesn’t glow, it reflect of the torch)
· Now ask the student to throw the light of torch on the white ball. It becomes bright. Ask the students:
__ Is the ball bright due to its own light? (Expected Response: no)
· Now light up the candle and ask the students:
—- is the light of candle of its own? (Expected response: yes.)
· Tell the students that some objects have their own light e. g. candle torch, stars and the Sun. Some objects have no light and they simply reflect the light of other objects .e. g. mirror, ball, Moon, and the earth.
· The objects which have their own light are called luminous objects and the objects which have no light of their own are called non—luminous objects.
· Ask a student to light up a torch and hold it. Instruct the others to see into the torch. Ask them: What is observed? (Expected response: A glowing bulb.)
· Inform them that as the bulb is emitting light, so the bulb is a luminous object.
· Guide them that cover of torch, so glass is transparent.
· Direct them to cover the glass with a tissue paper and ask: Is there any change in the torch light? (Expected response: It becomes less light.)
· Tell them that as light passes partially through the tissue paper, so tissue paper is translucent.
· Now ask them to cover the torch glass with a card board and ask: is any light seen through the cardboard? (Expected response: no light is seen.
· Tell them that light is totally blocked, so the card board is an opaque object.
· Ask the students to identify few more examples of opaque objects.
Sum up / Conclusion
· Objects that emit light of their own are known as luminous objects.
· Non-luminous object can be seen only when they are shone by the light.
· Moon is non-luminous and shines to give moonlight only when sunlight falls on it.
· The objects can be seen through transparent window glass.
· Objects on other side of the translucent objects can’t be seen clearly.
· All opaque objects block light and cause shadows.
Draw the following table on the board and ask the students to copy it in their notebooks and write their observations.
Does the material allow all of light/some light / or no light to pass through?
Types of material
· Involve the students in solving the questions given at the end of chapter / unit in textbook.
· Divide the class into three groups. Name them as A. B and C.
· Provide a piece of window glass covered with plastic tape on all its edges to group A
· Provide a wax paper to group B and a hard card board or wooden piece to group C.
· Place a lighted candle on the table top.
· Ask the groups to hold their objects in front of candle flame turn by turn and see the candle flame through the objects.
· Sum up their observations to reach the following conclusions.
Group A: As light passes through glass, so glass is transparent.
Group B: Candle behind the wax paper is not so clear as some light passes through it. Therefor materials like wax paper are translucent.
Group C: The light is totally blocked by the hard card board so it is opaque.
As the class to prepare a list of luminous, non-luminous, transparent, translucent and opaque objects which are being used by his/her family. Ask them to record their names in the notebook in the form of the given table.
Non – Luminous