Page 1 - Competency Based Worksheet- Light and its associated phenomena
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SAI INTERNATIONAL SCHOOL


                                                      Class 7
                                         Competency Based Worksheet
                                                 Subject- Physics
                                    Ch. – Light and Associated Phenomena

           For Assertion& Reason question follow the following directions.
           (a) If both Assertion and Reason are correct and Reason is the correct explanation of
           Assertion.
           (b) If both Assertion and Reason are correct, but Reason is not the correct explanation of
           Assertion
           (c) If Assertion is correct but Reason is incorrect
           (d) If Assertion is incorrect but Reason is correct
           (e) If Assertion & Reason both are incorrect
               1.    Assertion (A): A convex mirror is used as a rear-view mirror in vehicles.
                    Reason (R): Convex mirrors always form real and enlarged images.
               2.    Assertion (A): Light refracts when it enters water from air.
                    Reason (R): The speed of light increases when it enters a denser medium.
               3.    Assertion (A): In a plane mirror, the image appears to be laterally inverted.
                    Reason (R): The mirror reverses the top and bottom of an object.
               4.    Ria conducts an experiment using a glass prism, a torch, and a white screen. When
                    she passes white light through the prism, she observes seven colours on the screen
                    arranged in a band.

                        a)  What phenomenon is Ria demonstrating?
                             i)   Refraction
                             ii)   Dispersion
                             iii)   Reflection
                             iv)  Diffusion
                        b)  Which of the following best explains why different colours emerge?
                             i)   All colours reflect at the same angle.
                             ii)   Each colour of light has a different speed in glass.
                             iii)   Light is scattered in the air.
                             iv)  The screen absorbs some colours and reflects others.
                        c)  Which colour bends the most in this experiment?
               5.    During a science fair, a student spins a Newton’s disc rapidly, and surprisingly, the
                    coloured disc appears white.
                        a)  What principle is demonstrated here?
                        b)  Explain how this proves that white light is made of different colours.

               6.    You shine a laser beam at a concave mirror and adjust the angle so that the
                    reflected ray returns along the same path.
                        a)  What can you infer about the incident ray?
                        b)  How is the angle of incidence related to the angle of reflection?

               7.    A person uses a magnifying glass to read small text.
                        a)  What type of lens is used here?
                        b)  How does the lens help in magnifying the text?
                        c)  Why can't a concave lens be used for this purpose?

               8.    David is observing his image in a plane mirror. The distance between the mirror and
                    his image is 4 meters. If he moves 1 meter closer to the mirror, what will be the new
                    distance between David and his image?
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