NCERT 6th Class (CBSE) Science: Light, Shadows and Reflections

Question: Draw a diagram to illustrate the formation of umbra and penumbra.

Answer:

Question: What are the essential conditions for the formation of shadow?

Answer:

1.  There should be an opaque material.
2.  There should be a source of light and screen.

The object must be placed in the path of light. Then shadow is formed on the screen.

Question: Define reflection of light.

Answer: When light rays after striking the smooth and shiny surface return to same medium, this phenomenon is called reflection of light.

Question: How will you convert a glass sheet into a translucent sheet?

Answer: There are following two methods to convert glass sheet into a translucent sheet:

1.  By smearing a thin layer of oil on glass sheet.
2.  By covering a side of sheet by butter paper.

Question: What is shadow? How does the colour of an opaque object affects the colour of the shadow?

Answer: A dark outline or patch formed by an opaque object that blocks light coming from a source of light is called shadow. The colour of an opaque object does not affect the colour of the shadow.

Question: Write the differences between umbra and penumbra.

Answer:

Umbra:

1. It is the darkest part of shadow.
2. No light reaches to this region.
3. It is central part of a shadow.

Penumbra:

1. It is less dark part of shadow.
2. Light from some part of the source reaches.
3. It is outer part of a shadow.

Question: What do we need in order to see a shadow?

Answer: We need:

1.  A source of light
2.  A screen
3.  An opaque object.

Question: What do you mean by scattering of light?

Answer: When a beam of light falls on a rough surface it is turned back in different directions. It is called scattering of light.