p.8
Dispersion of White Light by Prism
What did Newton discover about sunlight using prisms?
Sunlight is made up of seven colors.
p.6
Dispersion of White Light by Prism
How should the glass prism be placed on the paper?
It should rest on its triangular base.
p.8
Atmospheric Refraction
What causes the apparent wavering of objects seen through hot air?
The difference in density and refractive index between hot and cooler air.
What causes the twinkling effect of stars?
The flickering of starlight entering the eye due to atmospheric refraction.
p.2
Function of the Lens in Human Eye
How does the brain process visual information?
By interpreting electrical signals sent via the optic nerves.
p.2
Function of the Lens in Human Eye
What is the role of light-sensitive cells in the retina?
They get activated upon illumination and generate electrical signals.
p.7
Dispersion of White Light by Prism
What is the acronym used to remember the sequence of colors in a rainbow?
VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange, Red).
p.10
Colour of the Sky and Sun at Sunrise/Sunset
What would the sky look like without an atmosphere?
The sky would appear dark due to the lack of scattering.
p.1
Function of the Lens in Human Eye
What is the role of the cornea in the human eye?
It allows light to enter and provides most of the refraction.
p.1
Function of the Lens in Human Eye
What is the function of the iris in the human eye?
To control the size of the pupil and regulate light entry.
p.5
Importance of Eye Donation
How long does the eye removal process take?
It takes only 10-15 minutes.
p.3
Defects of Vision and Correction
How is myopia corrected?
By using a concave lens of suitable power.
p.12
Power of Accommodation
Why is a normal eye not able to see clearly objects placed closer than 25 cm?
Because it cannot accommodate enough to focus on closer objects.
p.10
Colour of the Sky and Sun at Sunrise/Sunset
What happens to sunlight as it passes through the atmosphere?
Fine particles in the air scatter blue light more strongly than red light.
p.6
Dispersion of White Light by Prism
What should be done after removing the pins and the glass prism?
Join the points E and F where the lines meet the boundary of the prism.
p.4
Defects of Vision and Correction
What causes hypermetropia?
Either the focal length of the eye lens is too long or the eyeball is too small.
p.4
Defects of Vision and Correction
What causes presbyopia?
Weakening of the ciliary muscles and diminishing flexibility of the eye lens.
p.3
Defects of Vision and Correction
What causes the image of a distant object to form in front of the retina in myopia?
Excessive curvature of the eye lens or elongation of the eyeball.
p.12
Colour of the Sky and Sun at Sunrise/Sunset
Why does the Sun appear reddish early in the morning?
Due to scattering of light in the atmosphere.
p.6
Dispersion of White Light by Prism
What is the first step in the activity involving a glass prism?
Fix a sheet of white paper on a drawing board using drawing pins.
p.8
Dispersion of White Light by Prism
What role do water droplets play in the formation of a rainbow?
They act like small prisms that refract and disperse sunlight.
p.1
Function of the Lens in Human Eye
What is the retina in the human eye?
A light-sensitive screen where images are formed.
p.6
Dispersion of White Light by Prism
What is the purpose of fixing pins at points P and Q?
To look for the images of the pins through the other face AC of the prism.
p.6
Dispersion of White Light by Prism
What happens to the light ray when it enters from air to glass?
The light ray bends towards the normal.
p.6
Dispersion of White Light by Prism
What occurs when the light ray exits from glass to air?
The light ray bends away from the normal.
p.4
Defects of Vision and Correction
What is presbyopia?
A defect where the near point gradually recedes due to aging.
p.1
Human Eye and Vision Correction
What happens to our ability to identify colors when our eyes are closed?
It becomes impossible to identify colors.
p.5
Refraction of Light through a Prism
What shape does a triangular glass prism have?
It has two triangular bases and three rectangular lateral surfaces.
p.12
Atmospheric Refraction
Why does the sky appear dark instead of blue to an astronaut?
Because there is no atmosphere to scatter light.
p.10
Colour of the Sky and Sun at Sunrise/Sunset
Why is the color of the clear sky blue?
Air molecules scatter shorter wavelengths of light, particularly blue, more effectively than longer wavelengths like red.
p.3
Human Eye and Vision Correction
What is one advantage of having two eyes for vision?
It provides a wider field of view.
p.10
Colour of the Sky and Sun at Sunrise/Sunset
Why are 'danger' signal lights red?
Red light is least scattered by fog or smoke, making it visible at a distance.
p.7
Dispersion of White Light by Prism
What happens when a second identical prism is placed in an inverted position to the first prism?
It recombines the spectrum back into white light.
p.4
Defects of Vision and Correction
What do bifocal lenses consist of?
Both concave and convex lenses.
p.11
Dispersion of White Light by Prism
What is dispersion in the context of light?
The splitting of white light into its component colors.
p.1
Human Eye and Vision Correction
What is the primary function of the human eye?
To enable us to see objects around us.
p.7
Dispersion of White Light by Prism
Why do different colors of light bend at different angles when passing through a prism?
Because each color has a different wavelength, causing them to refract differently.
p.9
Scattering of Light and Tyndall Effect
What types of particles contribute to the Tyndall effect in the atmosphere?
Smoke, tiny water droplets, suspended dust particles, and air molecules.
p.9
Scattering of Light and Tyndall Effect
What happens to the color of scattered light based on particle size?
Very fine particles scatter mainly blue light, while larger particles scatter longer wavelengths.
p.5
Importance of Eye Donation
What happens to unsuitable donated eyes?
They are used for valuable research and medical education.
p.2
Defects of Vision and Correction
How can vision be restored in cases of cataract?
Through cataract surgery.
p.8
Dispersion of White Light by Prism
In which direction is a rainbow always formed relative to the Sun?
In a direction opposite to that of the Sun.
p.6
Dispersion of White Light by Prism
What should be traced around the prism?
The outline of the prism using a pencil.
p.8
Atmospheric Refraction
What is atmospheric refraction?
The refraction of light by the Earth's atmosphere.
p.7
Dispersion of White Light by Prism
What are the colors observed when white light is dispersed by a prism?
Violet, Indigo, Blue, Green, Yellow, Orange, and Red.
p.9
Scattering of Light and Tyndall Effect
What is the Tyndall effect?
The scattering of light by colloidal particles, making the path of light visible.
p.3
Human Eye and Vision Correction
What happens to our perception of the world when one eye is shut?
The world looks flat and two-dimensional.
p.3
Defects of Vision and Correction
What are the three common refractive defects of vision?
Myopia, Hypermetropia, and Presbyopia.
p.1
Human Eye and Vision Correction
Why is the human eye considered the most significant sense organ?
Because it enables us to see the beautiful, colorful world.
p.12
Defects of Vision and Correction
What is the focal length of a lens with a power of +1.5 dioptres for near vision?
Focal length = 1/(+1.5) m = 0.667 m or 66.7 cm.
p.7
Dispersion of White Light by Prism
What phenomenon occurs when white light passes through a prism?
Dispersion of white light into a spectrum of colors.
p.5
Importance of Eye Donation
What can be done with our eyes after death?
They can be donated to help blind people.
p.5
Importance of Eye Donation
What percentage of corneal blindness can be cured through transplantation?
60% of the 4.5 million people with corneal blindness are children below the age of 12.
p.5
Importance of Eye Donation
Who can donate their eyes?
Anyone, regardless of age or sex, including those who wear spectacles or have had cataract surgery.
p.5
Importance of Eye Donation
What is the time frame for eye removal after death?
Eyes must be removed within 4-6 hours after death.
p.1
Function of the Lens in Human Eye
How does the crystalline lens assist in vision?
It provides finer adjustment of focal length for focusing.
p.12
Defects of Vision and Correction
What is the focal length of a lens with a power of -5.5 dioptres for distant vision?
Focal length = -1/(-5.5) m = 0.182 m or 18.2 cm.
p.5
Refraction of Light through a Prism
How does light behave when refracted through a rectangular glass slab?
The emergent ray is parallel to the incident ray but slightly displaced laterally.
Why don't planets twinkle like stars?
Planets are closer to Earth and appear as extended sources, averaging out the light variations.
p.2
Defects of Vision and Correction
What can lead to significant loss of visual functioning?
Damage to any part of the visual system.
p.10
Colour of the Sky and Sun at Sunrise/Sunset
What color does the Sun appear at sunrise and sunset?
The Sun and surrounding sky appear red.
p.10
Scattering of Light and Tyndall Effect
What is observed when sodium thiosulphate is dissolved in water during the activity?
Fine microscopic sulphur particles precipitate, scattering blue light.
p.10
Scattering of Light and Tyndall Effect
What color is observed from the fourth side of the glass tank during the activity?
Initially orange-red, then bright crimson red.
p.12
Function of the Lens in Human Eye
What causes the change in focal length of the eye lens?
The action of the ciliary muscles.
Why do planets not twinkle?
Because they are closer and appear as point sources of light.
p.10
Colour of the Sky and Sun at Sunrise/Sunset
Why do passengers flying at high altitudes see a dark sky?
Scattering is not prominent at such heights.
p.6
Dispersion of White Light by Prism
What angles are marked in the activity?
Angle of incidence (∠i), angle of refraction (∠r), and angle of emergence (∠e).
Why does a star appear higher than its actual position when viewed near the horizon?
Due to atmospheric refraction bending starlight towards the normal.
p.2
Power of Accommodation
What is the function of the ciliary muscles?
They modify the curvature of the eye lens to change its focal length.
p.2
Power of Accommodation
What is accommodation in the context of the eye?
The ability of the eye lens to adjust its focal length.
p.12
Defects of Vision and Correction
What is the nature and power of the lens required for a myopic person whose far point is 80 cm?
A concave lens with a power of -1.25 dioptres.
Why do stars twinkle?
Due to atmospheric refraction of light.
p.4
Defects of Vision and Correction
What is the near point for a person with hypermetropia?
Farther away than the normal near point (25 cm).
p.2
Power of Accommodation
What happens to the pupil in bright light?
The iris contracts the pupil to allow less light to enter.
What causes the apparent position of a star to fluctuate?
The changing physical conditions of the Earth's atmosphere.
p.11
Colour of the Sky and Sun at Sunrise/Sunset
Why does the Sun appear reddish at sunrise and sunset?
Because light passes through thicker layers of air, scattering shorter wavelengths and allowing longer wavelengths to reach our eyes.
p.11
Power of Accommodation
What is the ability of the eye to focus on both near and distant objects called?
Accommodation of the eye.
p.11
Defects of Vision and Correction
How is myopia (short-sightedness) corrected?
Using a concave lens of suitable power.
p.12
Function of the Lens in Human Eye
What happens to the image distance in the eye when the distance of an object increases?
The image distance increases as the object moves further away.
p.4
Defects of Vision and Correction
How can hypermetropia be corrected?
By using a convex lens of appropriate power.
p.6
Dispersion of White Light by Prism
What is the angle called that measures the bending of the emergent ray?
The angle of deviation (∠D).
p.9
Scattering of Light and Tyndall Effect
What is observed when sunlight passes through a smoke-filled room?
The path of the beam becomes visible due to scattering of light.
p.11
Defects of Vision and Correction
What are the common refractive defects of vision?
Myopia, hypermetropia, and presbyopia.
p.11
Defects of Vision and Correction
How is hypermetropia (far-sightedness) corrected?
Using a convex lens of suitable power.
