LIGHT:REFLECTION AND REFRACTION-II:BRIEF ANSWERS

ANSWER IN BRIEF

*INDEX-TOPIC SEARCH

1. EXPLAIN THE NATURE OF LIGHT IN BRIEF
   

   ANS:
   

   • Light is an electromagnetic radiation in the form of waves and it does not require material medium for its propagation.
   • Light travels at the speed of 3 x 10⁸ m/s in vacuum.
   • When it passes through a transparent medium its speed reduces significantly.
   • The wavelength of visible light is 4 x 10^(-7) to 8 x 10^(-7) m.
   • Light incident on a surface separating two media is partly reflected, partly refracted(transmitted), and partly absorbed.
   • Highly polished surface reflects a large amount of incident light whereas a transparent medium refracts(transmits) most of the light incident on it.
   • A lens or mirror focuses light falling on it because of reflection or refraction.
   • Due to reflection by a mirror or refraction by a lens, the image of an object is formed or it appears to have formed.
   
   



2. EXPLAIN:REGULAR AND IRREGULAR REFLECTION
   

   ANS:When light is incident on an opaque surface,reflection occurs.There are two types of reflection:(i)Regular reflection and (ii)Irregular reflection.
   
   
   
   Regular Reflection:When a parallel beam of light falls on a smooth or highly polished (opaque) surface, the reflected beam is also parallel and directed in a fixed direction.This type of reflection is called regular reflection.For example,reflection by a mirror. Regular reflection does not enable us to see the object.
   
   Irregular Reflection:When a parallel beam of light falls on a rough surface, the reflected beam is not parallel and it spreads over a wide area. This is called irregular reflection.Irregular reflection enables us to see the object.
   



3. STATE LAWS OF REFLECTION
   

   ANS:The laws of reflection are:
   
   

   • The angle of incidence(θ_i) is equal to the angle of reflection(θ_r).
   
   
   • The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane.
   
   



4. EXPLAIN : Real image and virtual image.
   

   ANS:
   
   

   
   
5. MENTION CHARACTERISTICS OF IMAGE FORMED BY A PLANE MIRROR.
   

   ANS:

   
   
   • The image is virtual, erect and of the same size as the object.
   • The image is at the same distance behind the mirror as the object is in front of the mirror.
   • The image is laterally inverted,i.e., when a person raises the left hand the image appears to raise the right hand.
     

   
   

   
   
6. Draw the ray diagram to show the position, nature and the size of the image when object is placed at infinity from a concave mirror.
   

   ANS:
   
   
   
   The image is formed at focus(F); it is real, inverted and highly diminished.



7. Draw the ray diagram to show the position, nature and the size of the image when object is placed beyond C (Center of curvature) of a concave mirror.
   

   ANS:
   
   
   
   The image is formed between focus(F) and center of curvature(C); it is real, inverted and diminished.



8. Draw the ray diagram to show the position, nature and the size of the image when object is placed at C (Center of Curvature)of a concave mirror.
   

   ANS:
   
   
   
   The image is formed at C; it is real, inverted and of the same size as the object.



9. Draw the ray diagram to show the position, nature and the size of the image when object is placed between C and F of a concave mirror.
   

   ANS:
   
   
   
   The image is formed beyond C; it is real, inverted and enlarged.



10. Draw the ray diagram to show the position, nature and the size of the image when object is placed at focus(F) of a concave mirror.
    

    ANS:
    
    
    
    The image is formed at infinite distance; it is real, inverted and highly enlarged.



11. Draw the ray diagram to show the position, nature and the size of the image when object is placed between pole(P) and F of a concave mirror.
    

    ANS:
    
    
    
    The image is formed behind the mirror; it is virtual and erect and enlarged.



12. Draw the ray diagram to show the position, nature and the size of the image when object is placed at infinity from a convex mirror.
    

    ANS:
    
    
    
    The image is formed at the focus F behind the mirror; it is virtual and erect and highly diminished.



13. Draw the ray diagram to show the position, nature and the size of the image when object is placed between pole(P) of a convex mirror and infinity.
    

    ANS:
    
    
    
    The image is formed between P and F behind the mirror; it is virtual and erect and diminished.



14. Draw the ray diagram to show the position, nature and the size of the image when object is placed at infinity from a convex lens.
    

    ANS:
    
    
    The image is formed on the opposite side of lens at focus (F₂); it is real and inverted and highly diminished(point-sized).



15. Draw the ray diagram to show the position, nature and the size of the image when object is placed beyond 2F₁ of a convex lens.
    

    ANS:
    
    
    
    The image is formed between F₂ and 2F₂of the lens; it is real, inverted and diminished.



16. Draw the ray diagram to show the position, nature and the size of the image when object is placed at 2F₁ of a convex lens.
    

    ANS:
    
    
    
    The image is formed at 2F₂; it is real inverted and of same size as the object.



17. Draw the ray diagram to show the position, nature and the size of the image when object is placed between F₁ and 2F₁ of a convex lens.
    

    ANS:
    
    
    
    The image is formed beyond 2F₂; it is real, inverted and enlarged.



18. Draw the ray diagram to show the position, nature and the size of the image when object is placed at F₁ of a convex lens.
    

    ANS:
    
    
    
    The image is formed at infinity; it is real, inverted and highly enlarged.



19. Draw the ray diagram to show the position, nature and the size of the image when object is placed between F₁ and optical center O of a convex lens.
    

    ANS:
    
    
    
    The image is formed on the same side of the lens as the object; it is virtual,erect and enlarged.



20. Draw the ray diagram to show the position, nature and the size of the image when object is placed at infinity from a concave lens.
    

    ANS:
    
    
    
    The image is formed at the focus F₁ on the same side of the object; it is virtual, erect and highly diminished.



21. Draw the ray diagram to show the position, nature and the size of the image when object is placed between infinity and the optical center O of a concave lens.
    

    ANS:
    
    
    
    The image is formed between focus F₁ and the optical center O on the same side of the object; it is virtual, erect and diminished.



22. STATE LAWS OF REFRACTION.
    

    ANS:The laws of refraction are:
    
    

    • The ratio of the sine of the angle of incidence(θ₁) to the sine of the angle of refraction(θ₂) is constant.
    
    
    • The incident ray, the normal to the surface separating two mediums and the refracted ray, all lie in the same plane.
    
    



23. DISTINGUISH BETWEEN REFLECTION AND REFRACTION.
    

    ANS:
    
    



24. STATE SNELL'S LAW AND WRITE ITS FORMULA.
    

    ANS:The ratio of the sine of the angle of incidence and the sine of the angle of refraction is always constant for given pair of mediums.
    
    sinΘ₁/sinΘ₂ = constant
    
    The constant is known as the refractive index of medium 2 with respect to medium 1, and is denoted by η₂₁

    
    
25. THE REFRACTIVE INDEX OF TWO MEDIUMS A AND B ARE 1.33 AND 1.5, RESPECTIVELY.
    1. IF A RAY TRAVELS FROM A TO B, WHAT WILL HAPPEN TO ITS SPEED?
    2. WILL TOTAL INTERNAL REFLECTION OCCUR IF A RAY TRAVELS FROM A TO B?
       
    
    

    ANS:

    
    
    1. The speed of the light ray will decrease as it enters a denser medium from a rarer medium.
    2. No, total internal reflection will not occur because the ray will move towards the normal in this case.