IMPORTANT QUESTIONS (X) ...!!!!

                                                 MCQ's

1. Four students A,B,C,D perform experiment on tracing the path of light ray through a glass slab. The position of the pins used to describe incident way is shown on paper by four of them, respectively as:

   

   'c' option is correct

   
   

   
   

   
   

   2)Teacher asked three students to write one precaution by each of them regarding the experiment on  tracing the path of the light ray through glass slab. First, second and third student wrote down the following precautions, respectively
    (a) While tracing emergent ray, we should see heads of pins.
    (b) One eye should be kept closed, while tracing emergent ray
    (c) Glass slab should have parallel edges.
          The correct statements are of
          (i) 1 and 2             (ii) 2 and 3                (iii) 1 and 3                 (iv) All three
   
   
          3) A student is asked to label his diagram made as observation on tracing the path of light ray 
             through glass slab as follows:
      
   The correct sequence of labelling angle I, angle e , angle r and lateral displacement respectively is,
   1. (a) 1,2,3 and 4                          (b) 3,4,1 and 2
      (c) 1,3,2 and 4                          (d) 3,2,4 and 1
      
      
      4) A student obtains an image of window by using a convex lens on a screen. He adjusts the position of screen to get sharpest and brightest image possible. To get focal length of lens he should measure the:
      (a) distance between window and screen
      (b) distance between convex lens and window.
      (c) distance between screen and convex lens
      (d) distance between window and convex lens as well as distance between window and screen.
       
   5)A student determines the focal length of a device 'X' by focusing the image of a distant object on a screen placed on the same side as the object. The device 'X' is.                                                       (a) Concave lens             (b) Convex lens     (c) Concave mirror           (d) Convex mirror   
2. 
   
   
   1. QUESTION / ANSWERS 
      Ques1: Name the part of the human eye that helps in changing the focal length of the lens?
      Ans: Ciliary Muscles
      
      
      Ques2:What is the cause of dispersion of white light passing through a prism? Which colour of light deviates the-
       (i) most ; (ii) least
      Ans: Each colour in VIBGYOR has different refractive index or speed in glass medium of prism. Red have least value of refractive index and violet has the maximum.                                                                                                                                                                                                                                                                                         Ques3: Why does the clear sky appear blue? How would the sky appear in the absence of earth's atmosphere?                                                                                                                Ans:Scattering of molecules of gases in atmosphere makes the colour of sky appear blue. In absence of atmosphere of earth no scattering will be there as a result sky will appear Black.                                                                                                                                                                                                                                                            Ques4: How can you identify three types of mirrors without touching?                                                                                                                                  Ans: By looking into mirror by going close to it. If image is of same size and erect then it is Plane mirror. If image is of bigger size and erect then it is Concave mirror. If image is of smaller size and erect then it is convex mirror.                                                                                                                                                                                                                                     
      Ques5: A real image, 1/5^th the size of object is formed at a distance of 18cm from a mirror. What is the nature of mirror? Calculate its focal length.                                                              Ans: Real image means it is concave mirror. m = -1/5 = -(-18)/u ==> u= -90                        Now use 1/f = 1/u + 1/v ==> f= -15                                                                                                                                                                                                                                    
      Ques6: A ray of light is incident obliquely on a glass slab. Draw a ray- diagram showing the path of the light ray. Clearly mark angle of incidence, angle of refraction, angle of emergence and lateral displacement of the ray. Give a formula to find refractive index of glass slab in terms of angle of incidence and angle of refraction.
      Ans:
       
                                                        
             
      Ques7: A person cannot see objects farther than 12m from the eye clearly. Name the,defect of vision he is suffering from and the lens that shouls be used for correction of this defect. Illustrate with the help of a diagrams, How this lens will correct the defective vision.
      Ans: 
      
        
      Ques8: Draw a ray diagram in each of the following cases to show the formation of image, when object is placed:
      (a) Between optical centre and principal focus of a convex lens.
      (b) Between F and 2F of a concave lens
      100. At 2F of a convex lens
      What can you say about sign and value of linear magnification ratio in, (i) and (ii) above.
                                                                                                                                                                                                                    
      Ques9: (i)Define real image of an object.
      2. Name the mirror that
         (a) can give real as well as virtual image of an object.
      (b) will always give virtual image of same size of an object.
      (c) will always give virtual and diminished image of an object.
      (d) is used by a doctor in examining teeth.
      (iii) With the help of a ray diagram explain the use of concave mirror as solar concentrators.
      Ans: (i) If reflected or refracted meet actually, the point of intersection is called real image of point object. (ii) (a) concave (b) plane mirror  (c) convex mirror     (d) concave
      
                                                
      Ray coming parallel to principal axis will pass through principal focus.