सूर्य जैसी वस्तुओं को दीप्तिमान (luminous) वस्तुएं कहा जाता है। उन्हें ऐसा कहने का सही कारण निम्नलिखित में से कौन सा है?

Shadows are formed when an _______ object comes in the path of light.

If you are asked to project the real image of a well-lit painting on a wall, which one of the following optical devices would you select for this purpose?

Which of the following statements is correct on the basis of the following information? 'A' always forms a virtual and erect image. 'B' forms a real and inverted image in most cases.