These comprehensive RBSE Class 10 Science Notes Chapter 11 Human Eye and Colourful World will give a brief overview of all the concepts.
RBSE Class 10 Science Chapter 11 Notes Human Eye and Colourful World
→ Human’s Eye – The human eye is one of the most valuable and sensitive organs. The human eye is like a camera.
→ Main parts of human eye-(a) Cornea (b) Iris (c) Eye lens (d) Pupil (e) Ciliary muscles (f) Retina (g) Optic nerves (h) Sclerotic (i) Vitreous humour (j) Aqueous humour.
→ The eye lens forms and inverted real image of the object on the retina.
→ Power of Accommodation-It is the ability of eye lens to adjust the focal length to form a sharp image of the object at different position on retina.
→ The minimum distance, at which objects can be seen most distinctly without strain is called the least distance of distinct vision. It is also called the near point of the eye. For a young adult with normal vision, the near point is about 25 cm. The farthest point upto which the eye can see objects clearly is called the far point of the eye. It is infinity for a normal eye.
→ Range of Vision-Range of vision is the distance between near point and far point. It is 25 cm to infinity for normal human eye.
→ Damage to or malfunction of any part of the visual system can lead to significant loss of visual functioning.
→ Defects of eye and their remedies –
(i) Myopia or short sightedness – It is a type of defect in which the person cannot see distant objects clearly. It can be corrected by using a concave lens or diverging lens of correct focal length.
(ii) Hypermetropia or far sightedness – It is a type of defect in which a person cannot see nearby objects clearly. It can be corrected by using a convex lens or converging lens of correct focal length.
(iii) Presbyopia – It is a type of defect in which a person cannot see near and distant objects clearly. It can be rectified by using a bifocal lens.
→ Refraction of light through a prism – Two inclined surfaces which participate in the process of refraction are called refracting surfaces. Angle between two refracting surface is called angle of refraction or angle of prism. It is represented by A.
→ Angle of deviation through a prism –
- The peculiar shape of the prism makes the emergent ray. bend at an angle to the direction of the incident ray. This angle is Prism called the angle of deviation.
- Angle of deviation of different colours of light is also different.
- Angle of deviation of red colour is minimum and that of violet colour is maximum.
→ Dispersion of white light through glass prism –
(i) The band of seven colours obtained by passing white light through prism is called spectrum.
(ii) The splitting of white light into its seven component colours is called as dispersion. The seven colours are violet, indigo, blue, green, yellow, orange and red i.e. VIBGYOR. The splitting of light into its component colours is called dispersion.
→ Just after rain, when sunlight falls on the tiny droplets of water present in the atmosphere, at that time due to the dispersion of sunlight, rainbow is formed in the sky.
→ Conditions when rainbow is seen-We can see a rainbow just after rain.
→ Atmospheric Refraction-When the light radiations coming from the sun enters in earth’s atmosphere it undergoes refraction due to passing from different layers of atmosphere from rarer to denser medium. The process of refraction in the atmosphere, is termed as atmospheric refraction.
→ Some of the natural phenomenon based on atmospheric refraction are (i) Twinkling of stars. (ii) Visibility of sun before 2 minutes of actual sunrise and after 2 minutes of actual sunset. (iii) Oval appearance of sun at the time of sunrise and sunset and circular during noon.
→ Scattering of light – As sunlight travels through the earth’s atmosphere, much of the light is absorbed by tiny dust particles, air molecules and atoms and molecules of varidus gases present in atmosphere which scatters the absorbed light in various direction. This phenomenon is called scattering of light.
→ Tyndall effect – The phenomenon of scattering of light by the colloidal particles like dust particles, smoke, water droplets is called tyndall effect.
→ In the absence of atmosphere, the colour of the sky appears black even in the day time. Sky appears blue due to the scattering of blue coloured light maximum.
→ Blue colour of the sky and red colour of sun at the time of sunset and sunrise are due to scattering of light.
→ The danger signal light is red in colour because red is least scattered by fog or smoke. Therefore, it can be seen in the same colour at a distance.
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