Grade 8 Physics ยท Complete all 5 exercises, play the game, then submit your work.
๐ Student Information
โฑ A timer starts when you begin. Work carefully โ quality matters more than speed.
Exercise 1 โ Light Sources
Identify luminous objects and properties of light. (2 pts)
Q1 ยท Which object is a luminous source of light?
โ Correct! The Sun produces its own light โ it is luminous.
โ The Moon and mirror only reflect light โ they are non-luminous.
Q2 ยท Light travels inโฆ
โ Correct! Light travels in straight lines โ this is called rectilinear propagation.
โ Light always travels in straight lines (rectilinear propagation) in a uniform medium.
Exercise 2 โ Shadow Formation
Study the diagram below and answer the questions. (3 pts + journal)
๐ผ Shadow Scene โ Study this diagram
Q1 ยท Where does the shadow form?
โ Correct! The shadow is a dark region on the screen where light is blocked by the opaque object.
โ The shadow always forms on the opposite side of the light source, behind the opaque object.
Q2 ยท Which statement correctly describes the shadow diagram?
โ Correct! The umbra is the region of total darkness in a shadow.
โ The umbra is the fully dark region of a shadow where no light reaches at all.
๐ Lab Journal โ Observation (teacher-read)
Describe in 2โ3 sentences: what happens to the shadow's size when you move the light source closer to the object?
Q3 ยท A small point-source lamp creates a shadow. The shadow edge isโฆ
โ Correct! A point source creates only a pure umbra โ no partial shadow (penumbra).
โ A point source has no width, so it produces only a sharp-edged umbra, no penumbra.
Exercise 3 โ Ray Diagrams
Draw light rays on the canvas, then answer three questions. (4 pts)
โ๏ธ Draw the ray diagram โ show how light from the lamp casts a shadow
Draw at least 2 arrows showing rays from the lamp being blocked by the object to form a shadow on the screen.
Colour:Size:
Q1 ยท What does an arrow on a light ray represent?
โ Correct! Arrows on rays show the direction of light travel.
โ In ray diagrams, arrows always show the direction in which the light is travelling.
Q2 ยท Why do we draw light as straight lines with arrows?
โ Correct! Straight lines reflect rectilinear propagation of light.
โ We draw straight lines because light propagates in straight lines through uniform media.
Q3 ยท When a ray of light hits an opaque object, itโฆ
โ Correct! Opaque objects block light, forming a shadow.
โ Opaque objects absorb or reflect light โ rays cannot pass through, so a shadow forms behind.
๐ฎ Shadow Quiz Game
5 questions ยท 10 s each ยท 3 lives ยท Score adds bonus points to your grade!
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Game Over!
Exercise 4 โ Reflection & the Protractor
Measure the angle of reflection, then answer questions. (4 pts)
๐ Protractor Task โ Click on the canvas to draw the reflected ray
The mirror is the horizontal line. The normal is shown dashed vertically. The incident ray arrives from the upper-left. Click anywhere above the mirror on the right side to set your reflected ray, then click Check Angle.
๐ก Hint: The law of reflection says angle of incidence = angle of reflection. Both angles are measured from the normal (the dashed vertical line), not from the mirror surface.
Q1 ยท The law of reflection states that the angle of incidenceโฆ
โ Correct! Angle of incidence = angle of reflection โ this is the law of reflection.
โ The law of reflection: angle of incidence = angle of reflection (both measured from the normal).
Q2 ยท Angles of incidence and reflection are measured fromโฆ
โ Correct! The normal is the reference line โ always perpendicular to the mirror surface.
โ Both angles are measured from the normal โ the imaginary line perpendicular to the mirror.
Q3 ยท A ray hits a flat mirror at 30ยฐ to the normal. The reflected ray makes an angle of ___ with the normal.
โ Correct! 30ยฐ in = 30ยฐ out, by the law of reflection.
โ The angle of reflection equals the angle of incidence, so 30ยฐ โ 30ยฐ.
Exercise 5 โ MCQ & Reflection Labelling
Three multiple-choice questions plus a diagram labelling task. (4 pts)
MCQ 1 ยท Which surface reflects light most effectively?
โ Correct! Smooth, polished surfaces produce specular (regular) reflection.
โ Polished/smooth surfaces give specular reflection โ the most effective type of reflection.