Unit 5 Shadows
question 5.1
3: We can do more experiment about light to collect more evidence.
1: When the cardboard is straight you can see light at the other end and when it's bend you cannot see it at the other end.
2: light goes at a straight line.
Shadows
When light is stopped or blocked by some types of solid object, it cannot shine through the object. A shadow forms on the other side of the solid object.
Question 5.1b
1: I can identify the object
2: 
Which material let light through
A shadow forms when light is blocked by a opaque object. Some object are made of materials that allow light to pass through them. Objects that allow all the light to pass through are transparent. These do not form any shadow when a light shines on them. Objects that allow some light to pass through are translucent. These form a weak shadow when a light shines on them. The shadow is grey rather than black.
Question 5.2
3: glass and plate, transparent materials lets all the light pass through, translucent material lets some light go through and opaque materials doesn't let any light go pass through.
1: opaque material did not let light pass through
2: You have to use the same source of light.
5.3 silhouettes and shadow puppets
What is a silhouettes?
An opaque object held between a light source and a screen gives you a shadow on the screen. The shadow of the object is a silhouette.
shadow puppets
A shadow puppet uses a silhouette to represent the puppet.
5.3 Questions
2:The traditional indonesian source of light for shadow play is oil lamp but we use a torch for our shadow play.
1:
4: Opaque
3:You cannot use clear plastic to make shadow puppets because, clear plastic is transparent.
5.4 What affects the size of a shadow?
5.4 Question
The distance between the light source and the object.
The further the distance between the light source and the object, the smaller the size of the shadow.
1: The distance between light source and the screen is the factor that I kept the same. The factor that i changed is the distance between the shadow puppet and the light source.
Yes I think the repeating measurement is more reliable.
5.5 Investigating shadow length
5.5 Questions
3:The shadow started long in the early morning, became shorter up to 13:00 and then started to become longer again.
1:
2:The sun is closer in the morning and the evening.
5.6 Measuring Light Intensity
Grade 5 Science Measuring of Light Intensity
5.7 How scientist measured and understood light
Light intensity is a measure of the amount of light in an area. In the past, people measured light intensity in 'candlepower'. This was the amount of ligt given out by a candle. Today people measure light intensity with light meters.
Film makers must make sure the light intensity is exactly right for filming.
Many flowers and vegetables grown are grown in commercial greenhouses. Inside a greenhouse the temperature, amount of moisture and the light intensity are controlled.
Test match cricket has to be played in daylight. when the light intensity falls to a certain level the day's play come to an end.
Question 5.6
3: In a commercial greenhouse, plants need to grow as fast and as big as possible. For this they need to have the maximum amount of light needed for healthy growth.
1: predicted correctly that the candle gives the lowest light intensity, followed by the LED and then the light bulb.
2: To make the test fair, learners must try to read the book same distance away from each light source each time.
for hundreds of years, scientists have tried to explain and understand the things that they observed about light, and then anonther scientist would collect new evidence and change the idea.
Rainbows
You can see a rainbow when drops of water in the air are hit by sunlight at a certain angle.
How did scientist explain rainbows?
Aristotle was a greek scientist who lived in the fourth century BCE. He thought rainbows were caused by clouds reflecting sunlight at certain angles.
500 years later, the Islamic scientist, Ibn al-Haytham, thought the rainbow was like a reflection in a mirror. The cloud was like a mirror, with the sunlight reflecting off the cloud.
About 950 years ago, Shen Kuo, from china, suggested that the sunlight hit the rain to make rainbows.
The English scientist, Isaac Newton, was the first to explain the rainbow accurately, about 300 years ago. He showed that sunlight (also called white light) is made up of different colours. Our eyes don't see these colours seperately. Newton used a prism to demonstrate that white light is a mix of colours. When sunlight passes through a prism, it bends. This is called refraction. The angle of bending is different for various colours of light: red, orange, yellow, green, blue, indigo and violet. In a rainbow, every raindrop acts as a tiny prism. The sun shines through the raindrops and light is refracted, giving a rainbow.
Question 5.7
3: He showed that sunlight is made up of different colours.
2: a prism.
1:Aristole and Ibn al-Haytham.
Check your progress 5
Check your progress 5
1: When light from a light source is blocked by an opaque object a shadow forms.
2:
B: choose two of the material that are translucent: tinted glass and clear plastic wrap
C: choose one of the material that is transparent: clear glass.
A: choose two of the material that are opaque: tinfoil and Wooden block.
3:
A: a lamp.
B: a sheet.
C: He could move the puppet closer to the screen or he could move the lamp
further back
4:
B: Between midday and 16:00 the shadow becomes longer.
C: The shadow is longest at sunrise and sunset.
A:Between 08:00 and midday the shadow becomes shorter.
D: The shadow is shortest in the middle of the day.
5: Light travels in straight lines. There is a bend in the tunnel so that the light from the end of the tunnel cannot be seen at first. Once the boys travelled around the bend the light from the end of the tunnel can travel straight into their eyes.