Vision & Light: 51 MCQs with answers

Iris

The iris controls the size of the pupil, thereby regulating the amount of light entering the eye.

25 cm

For a normal eye, the near point is about 25 cm, which is the least distance for clear vision.

Dispersion

Dispersion is the phenomenon where white light separates into its constituent colours, typically seen through a prism.

Diaphragm

The diaphragm is not a part of the eye; the iris acts like a diaphragm. The eye has lens, retina, and cornea.

True

The pupil is indeed the black opening in the centre of the iris through which light enters the eye.

To refract light

The cornea is primarily responsible for refracting light as it enters the eye.

Retina

The retina contains photoreceptors (rods and cones) that detect light and color.

To focus light onto the retina

The lens focuses light onto the retina, allowing for clear vision.

To adjust the amount of light entering

The pupil adjusts to control the amount of light that enters the eye.

Lens

The lens changes shape to focus on objects at varying distances.

The range of light visible to the human eye

The visible spectrum refers to the range of light wavelengths that can be seen by the human eye.

Blue

Blue light has a shorter wavelength compared to red light, which is at the opposite end of the visible spectrum.

To control pupil size

The iris controls the size of the pupil, thereby regulating the amount of light entering the eye.

The area where the optic nerve exits

The blind spot is located where the optic nerve exits the eye, lacking photoreceptors.

Accommodation

Accommodation is the process by which the eye adjusts its lens to focus on objects at different distances.

To detect light and convert it into neural signals

The retina is responsible for detecting light and converting it into neural signals that are sent to the brain.

Retina

The retina contains photoreceptors called cones that are responsible for color vision.

To focus light onto the retina

The cornea helps to focus light onto the retina, playing a crucial role in vision.

Iris

The iris is the colored part of the eye that controls the size of the pupil.

To allow light to enter the eye

The pupil is the opening that allows light to enter the eye, enabling vision.

Ciliary muscles

Ciliary muscles contract and relax to change the curvature of the eye lens, thus adjusting its focal length.

Myopia

Myopia (nearsightedness) is corrected by a concave lens because it diverges light before it enters the eye, helping focus the image on the retina.

Red

In the visible spectrum, red light has the longest wavelength and violet the shortest.

Scattering of light

Blue light is scattered more than other colours by air molecules, making the sky appear blue.

Red light is scattered the least

During sunrise and sunset, light travels a longer path through the atmosphere, so most blue light is scattered away, leaving mainly red light.

Atmospheric refraction

Stars twinkle because their light undergoes atmospheric refraction, which varies due to changing air density.

Atmospheric refraction

Atmospheric refraction bends sunlight, making the Sun visible about 2 minutes before actual sunrise and after actual sunset.

Real and inverted

The eye lens forms a real, inverted image on the retina, which the brain interprets as erect.

Accommodation

Accommodation is the ability of the eye to adjust its focal length to see objects clearly at various distances.

Convex lens

Hypermetropia (farsightedness) is corrected by a convex lens, which converges light rays to help focus on the retina.

True

At noon, sunlight travels a relatively shorter path through the atmosphere, so less scattering occurs and the Sun appears white.

Objects absorb certain wavelengths and reflect others.

Objects appear in different colors because they absorb certain wavelengths of light and reflect others. The color we perceive is the wavelength that is reflected.

Through binocular vision and the convergence of the eyes.

The eye perceives depth and distance primarily through binocular vision, where both eyes work together, and the convergence of the eyes helps in judging distance.

The retina is responsible for converting light into neural signals.

The retina is crucial for vision as it contains photoreceptors (rods and cones) that convert light into neural signals for the brain to interpret.

It refracts light entering the eye.

The cornea is responsible for refracting (bending) light as it enters the eye, which is essential for focusing images on the retina.

Artificial light has a different spectrum than natural light.

We see colors differently under artificial light because artificial light sources emit different spectra compared to natural sunlight, affecting color perception.

Different wavelengths of light are refracted by different amounts.

Chromatic aberration occurs because different wavelengths of light are refracted by different amounts when passing through a lens, causing color distortion.

The ciliary muscles contract.

The lens of the eye changes shape to focus on near objects when the ciliary muscles contract, allowing the lens to become thicker for better focus.

It causes the sky to appear blue.

Atmospheric scattering causes shorter wavelengths of light (blue) to be scattered more than other colors, making the sky appear blue.

To regulate the amount of light entering the eye.

The primary function of the pupil is to regulate the amount of light that enters the eye, adjusting to different lighting conditions.

Cones

Cones are the photoreceptors in the retina responsible for color vision, while rods are more sensitive to light and help in low-light conditions.

Through the combination of signals from different types of cones

The correct option is true because the human eye contains three types of cone cells that are sensitive to different wavelengths of light, allowing the brain to interpret various colors based on the combination of signals received.

The perceived color can change due to the light spectrum

The correct option is true because the color of an object is influenced by the spectrum of light illuminating it, which can lead to different perceptions of color under varying lighting conditions.

Blue light is scattered more than other colors

The correct option is true because Rayleigh scattering causes shorter wavelengths of light, such as blue, to scatter more than longer wavelengths, making the sky appear blue.

By dilating the pupil to allow more light in

The correct option is true because in low light conditions, the pupil dilates to increase the amount of light entering the eye, aiding in better vision.

It filters out certain wavelengths of light

The correct option is true because the lens can slightly filter certain wavelengths of light, which may affect the perception of color by altering the spectrum that reaches the retina.

The type of photoreceptors activated in the retina

The type of photoreceptors activated in the retina determines how colors are perceived under different lighting conditions. Different light sources can activate different photoreceptors, leading to a change in the perceived color of the object.

Refraction index variation

The separation of colors when light passes through a prism is primarily due to the variation in the refractive index for different wavelengths of light, causing each color to bend at a different angle.

The lens flattens

To focus on distant objects, the ciliary muscles relax, causing the lens to flatten. This adjustment allows for a clearer image of faraway objects on the retina.

Hypermetropia; insufficient curvature of the lens

Hypermetropia, or farsightedness, occurs when the lens does not curve enough to focus on nearby objects, leading to difficulty seeing them clearly.

It creates a color cast on the object

Multiple light sources with varying color temperatures can create a color cast on an object, altering its perceived color due to the different spectral compositions of the light.