X physics full notes chapter 5
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X physics full notes chapter 5

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X physics full notes chapter 5 X physics full notes chapter 5 Document Transcript

  • Light- Reflection and RefractionKey learnings :1. When light falls on a body, it may be absorbed, may betransmitted or light may come back to the same medium.2. Reflection of a light means light waves are neithertransmitted nor absorbed but are deflected from the surfaceof the medium back into the same medium.3. Laws of Reflection:First law of reflection: The incident ray, the normal to thesurface at the point of incidence and the reflected ray, all liein the same plane.Second law of reflection: The angle of incidence is equalto the angle of reflection.4. Real image is obtained when the rays of light afterreflection, actually converge at a point. It can be obtainedon the screen and can be seen with the eye.5. Virtual image forms when rays of light do not actuallymeet, but appear to meet when produced backwards. Itcannot be obtained on the screen.6. Characteristics of the image formed by the plane mirror:i. The image formed by a plane mirror is always virtual anderect.ii. Size of image = Size of object and the image is laterallyinverted.iii. The image formed by the plane mirror is as far behindthe mirror as the object is in front.7. Lateral Inversion: The phenomenon due to which theright side of the object appears as left and the left side ofFor More School Notes & Projects Visit www.toppersarena.com
  • the object appears as right. That is the image is invertedsideways.8. A spherical mirror whose reflecting surface is curvedoutwards and polished on the inner spherical surface isconvex mirror.9. A spherical mirror whose reflecting surface is curvedinwards and polished on the outer spherical surface isconcave mirror.10. Concave mirror mostly forms real images, which can bereceived on the screen.11. Convex mirror forms virtual images, which cannot bereceived on the screen.12. Differentiating between a plane mirror, a concave mirrorand a convex mirror, without touching them:i) If the image formed is erect and is of same size as inreality then it is a plane mirror.ii) If the image formed is still erect but smaller in size then itis a convex mirror.iii) If the image is erect but magnified when mirror is closeto the object then it is a concave mirror.13. Solar concentrators use huge concave mirrors to focuslarge amounts of solar energy thereby producing hightemperature conditions in a solar power plant.14. Concave mirrors are used as shaving and make upmirrors.15. The centre of the reflecting surface of a spherical mirroris a point called the pole of the mirror and usuallyrepresented by P.For More School Notes & Projects Visit www.toppersarena.com
  • 16. The horizontal line passing through the centre ofcurvature and pole of the spherical mirror is known asPrincipal axis.17. The centre of curvature of a spherical mirror is thecentre of the hollow sphere of glass, of which the sphericalmirror is a part and usually represented by C.18. The radius of curvature of a spherical mirror is theradius of the hollowsphere of glass, of which the spherical mirror is a part andusually represented by R.19. The diameter of the reflecting surface that is twice theradius is called its aperture.20. Radius of curvature (R) = 2  focal length (f)21. Rules for ray diagram-i. The path of the reflected light ray depends upon how theincident ray is oriented with respect to the principal axis.ii. A ray of light parallel to the principal axis, after reflectionpass through the principal focus.iii. A ray of light passing through the principal focus of amirror becomes parallel to the principal axis of the mirror,on reflectioniv. A ray of light incident obliquely towards the pole of mirroris reflected obliquely as per the laws of reflectionv. A ray of light passing through centre of curvature of amirror is reflected back along the same path22. Image formation by a concave mirror for differentpositions of the objectFor More School Notes & Projects Visit www.toppersarena.com
  • 23. Nature, position and relative size of the image formedby a convexmirror:24. The ratio of the height of the image to the height of theobject is known as the magnification.25. Magnification is positive for virtual image and negativefor real image.26. The phenomenon of change in the path of light from onemedium to another is called refraction of light.27. The angle formed between the incident ray and thenormal is called angle of incidence and the angle formedFor More School Notes & Projects Visit www.toppersarena.com
  • between the refracted ray and the normal is called angle ofrefraction.28. The cause of refraction is the change in the speed oflight as it goes from one medium to another medium.29. Larger the difference in speeds of light, the greater willbe the angle of bending and vice-versa.30. When a ray of light passes from a rarer medium to adenser medium, it bends towards the normal. Also, theangle of incidence is greater than the angle of refraction.31. When a ray of light passes from a denser medium to ararer medium, it bends away from the normal. Also, theangle of incidence is less than the angle of refraction32. Laws of refraction:The first law of refraction: The incident ray, the refracted rayand the normalat the point of incidence all lie in the same plane.Second law of refraction: The ratio of the sine of angle ofincidence in thefirst medium to the sine of angle of refraction in the secondmedium is aconstant for a given pair of medium and for a givenwavelength of light.where n is a constant known as refractive index of thesecond medium withrespect to the first medium. This law is also called as Snell’sLaw33. The phenomenon of change in path of light in goingfrom one medium to another is called refraction of light.For More School Notes & Projects Visit www.toppersarena.com
  • 34. The ratio of speed of light in vacuum to the speed oflight in a medium is called the refractive index of themedium. It has no unit.35. When a ray of light traveling from a rarer to a densermedium slows down and bends towards the normal.36. When it travels from a denser medium to a rarermedium, it speeds up and bends away from the normal.37. The shifting of emergent ray sideways from the directionof original incident ray is called lateral displacement orlateral shift38. The extend of the lateral shift depends on- the angle of incidence,- the thickness of slab, and- Refractive index of the glass slab39. Lateral displacement is produced during refractionthrough a glass slab and not through a glass prism.40. The angle through which a ray of light deviates onpassing through a prism is called the angle of deviation.41. Convex lens is thicker at the middle than at the edges.42. Concave lens is thicker at the edges than at the middle.43. Convex lens converge the rays of light while concavelens diverges.44. As the object moves towards the optical centre ofconvex lens, the image moves away from the optical centreexcept when the object is placed between focus and opticalcentre of the lens.For More School Notes & Projects Visit www.toppersarena.com
  • 45. As the object moves towards the optical centre of theconvex lens, the size of image increases and it’s highlyenlarged when object is at focus.46. Power of a lens is the reciprocal of its focal length. TheSI unit of power of a lens is Dioptre.Top FormulaeFor More School Notes & Projects Visit www.toppersarena.com