Electromagnets are used for various purposes but I fathom in this instance, the questioner is asking about how electromagnetics can be used to attraction or repulsion.
Example, electromagnets are used for attraction in cranes which attach them to containers in order to lift them.
Meanwhile, Maglev trains use electromagnets repulsive properties.
        
             
        
        
        
Answer:
A
Explanation:
since the wooden bat is an opaque object placed after a translucent object, light will come through the plastic sheet but will be unable to go through the bat. hence the dark shadow of the bat on a lit sheet 
 
        
             
        
        
        
Answer:
P = 3.5 D
Explanation:
As we know that convex lens is to be used to make the near point of eye to be correct
So we will have

here we have


now plug in all values into the formula


now for power of lens


so the power in dioptre is 
P = 3.5 D
 
        
             
        
        
        
Chameleon's tongue is more fast than thought. Its long sticky tongue moves at an amazing ballistic speed which lashes out unsuspecting insects and bugs. Now let us see how fast it is.
GIven: 
acceleration of the chameleon's tongue- 260 m/s
2 for 20 ms
constant speed 30 ms
50 ms total time 
1/20 of a second
solution: 
<u>260</u> = <u>  n</u><u>  </u>
20       50
<u>20 n </u>= <u>13, 000</u>
20            20
n= 650 m/s