What are opaque materials?

Shadows are formed because light travels in _____ lines.

A dark shadow will be cast by a/an _____ object.

A _____ eclipse occurs when the shadow of the Earth falls on the Moon.

A pinhole camera forms a/an _____ (erect/inverted) image of an object on the screen.

A _____ always forms an image that is of the same size as the object.

Which of these are examples of luminous objects?

(i) Sun (ii) Firefly (iii) paper (iv) wood