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Practice each question, then open the answer or worked solution.
Observe the picture given in Fig. $11.1$ carefully.
A patch of light is obtained at B, when the torch is lighted as shown. Which of the following is kept at position A to get this patch of light?
Ans: The correct answer is (c) A mirror.
Explanation: Patch of light can be reflected only by a mirror and changes its direction.
A student observes a tree given in Fig. $11.2$ through a pinhole camera. Which of the diagrams given in Fig. $11.3$ (a) to (d), depicts the image seen by her correctly?
Ans: The correct answer is (b).
Explanation: The image formed will be left-right reversed and inverted.
Four students A, B, C and D looked through pipes of different shapes to see a candle flame as shown in Fig. $11.4$.
Who will be able to see the candle flame clearly?
Ans: The correct answer is (d) D.
Explanation: As we can see, only in figure D tube is straight. So, we can clearly see candle flame through tube D.
Which of the following is/are not always necessary to observe a shadow?
Ans: The correct answer is (a) Sun.
Explanation: Sun is a source of light and it can be replaced by any other source of light like, torch. Hence, the sun is not always necessary to observe a shadow.
Paheli observed the shadow of a tree at $8:00$ a.m., $12:00$ noon and $3:00$ p.m. Which of the following statements is closest to her observation about the shape and size of the shadow?
Ans: The correct option is (c) Both the size and shape of the shadow of the tree change.
Explanation: Here, the source of light is the sun. Sun changes its position at different points of time. Thus, accordingly the shape and size of the shadow of the tree change.
Which of the following can never form a circular shadow?
Ans: The correct answer is (c) A shoe box
Explanation: Shape of the shoe box is either rectangular or square.
Two students while sitting across a table looked down onto its top surface. They noticed that they could see their own and each other’s image. The table top is likely to be made of:
Ans: The correct answer is (c) Glass sheet.
Explanation: Glass sheet is transparent and all of the other objects are opaque and non-reflecting. Therefore, only glass sheets will reflect light properly to form images.