Students should refer to the below Human Eyes and Colourful World Class 10 notes prepared as per the latest curriculum issued by CBSE and NCERT. These notes and questions are really useful as they have been developed based on the most scoring topics and expected questions in upcoming examinations for Class 10. Human Eyes and Colourful World is an important topic in Science Class 10 which if understood properly can help students to get very good marks in class tests and exams.
Human Eyes and Colourful World Class 10 Notes and Questions PDF Download
Read the notes below which will help you to understand all important and difficult topics in this chapter. There are some topics in Human Eyes and Colourful World chapter which you should understand carefully as many questions can come from those parts. Our team of teachers have designed the revision notes so that its helpful for students to revise entire course prior to the class tests.
MCQ Questions Human Eyes and Colourful World Class 10 Science
• HUMAN EYE: – The human eye is the most sensitive part of the human body. By closing our eyes, we can sense some objects with their smell, taste, sound they make or by touching them but we cannot identify the colour without opening our eyes.
Example: – Fragrance of pink and red roses is the same but they have different colours.
Parts of human eyes: –
• Cornea – It is the outermost part of the eye, light enters from this part.
• Eye lens – It is a convex lens ,its curvature is controlled by ciliary muscles.
• Ciliary muscles – The ciliary muscles are involved in lens accommodation and help in changing the focus of the lens in order to see things near or far accordingly. When the muscles contract, the focal length decreases and vice versa
• Iris – The part of the eye which controls the size of the pupil. It gives colour to the eyes
• Pupil – The aperture of the pupil varies with the help of the iris. Pupil regulates and controls the amount of light entering the eye.
• Retina – The light -sensitive screen, where the image of any object is formed, is called retina. It converts images from the eye into electrical impulses that are sent along the optic nerve to the brain, to interpret as vision. It comprises of the rod and the cone cells. The image formed on the retina is real and inverted.
• Rods They are responsible for vision at low light levels (night vision).
• Cones The cones help in seeing colour but only when light is at a high level
• Optic nerve – The Optic Nerve is the largest sensory nerve of the eye. It carries impulses for sight from the retina to the brain.
When Light is bright => iris contract => less amount of light enters in eye
• When Light is dim => iris expands => more amount of light enters in eye
Power of accommodation: – The ability of eye lens to adjust its focal length is called accommodation.
The curvature of eye lens is modified by the ciliary muscles. Due to the change of curvature its focal length is also changed.
Distant object => ciliary muscles get relaxed => decreases the curvature of lens =>lens becomes thin => focal length is increased
Object is close to eyes => ciliary muscles get contraction => increases the curvature of lens=> lens becomes thicker=> focal length decreased
● The minimum distance that a normal eye can see clearly is called the near point of the eye. And the maximum distance is at infinity, it is called as the far point. For a young adult near point is 25cm and far point is infinity.
Defect of vision and their correction: –
In cataract the lens of the eye becomes opaque which leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes.
Symptoms may include faded colours, blurry or double vision, halos around light, trouble with bright lights, and trouble seeing at night .Mostly occurs with ageing Can be cured through surgery.
(2) MYOPIA / near -sightedness – -→ problem to see far – – -→ image formed in front of retina – -→
Corrected using concave lens
(3) HYPERMEMETROPIA / Far -sightedness – problem to see near – image formed behind the retina – -→ Corrected using convex lens
(4) PRESBYOPIA: – This defect of eye arises due to the (i) diminishing flexibility of eye lend (ii) weakening of ciliary muscles → corrected by bifocal lens
Dispersion of light by a glass prism: – The splitting of light into its component colours is called dispersion of light. A prism can split the incident white light into a band of colours. the sequence of colours is Violet, Indigo, Blue, Green, Yellow, Orange and Red. We remember it with “VIBGYOR”.
(5) The band of the coloured components of a light beam is called its spectrum.
(6) The red light bends the least while the violet the most.
Isaac Newton was the first to use a glass prism to obtain the spectrum of sunlight.
Recombination of dispersed spectrum of white light
Isaac Newton was a first to use two glass prism arrangements as shown in the figure above in which the second identical prism is inverted with respect to the first prism. He observed that the light passing through the second prism was white light due to recombination of the spectrum of light. This gave him the idea that the sunlight was made up of seven colours
Rainbow – A rainbow is a natural spectrum appearing in the sky after a rain shower. It is caused by dispersion of sunlight by tiny water droplets, present in the atmosphere. A rainbow is always formed in a direction opposite to that of the Sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop.
Atmospheric refraction – The refraction due to the atmosphere is called atmospheric refraction. Here due to the temperature difference between the air, refraction occurred. The hotter air is lighter (less dense) than the cooler air (denser) above it. Here refractive index of hotter air is slightly less than that of the cooler air.
Twinkling of stars
The twinkling of stars is a phenomenon due to the atmospheric refraction.
Advanced sunrise and delayed sunset- due to atmospheric refraction the Sun is visible to us about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset.
Scattering of light: – Scattering of light is the phenomenon in which light rays deviate from their original path upon striking an obstacle like dust or water droplets.
● Scattering of light makes the particles visible.
● Tyndall effect is the phenomenon of scattering of light by colloidal particles
● Colour of the sky appears Blue
● Danger signals are red in colour