Basic Science for Class 8 Science Chapter 1 - Food Production
Basic Science Solutions for Class 8 Science Chapter 1 Food Production are provided here with simple step-by-step explanations. These solutions for Food Production are extremely popular among Class 8 students for Science Food Production Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Basic Science Book of Class 8 Science Chapter 1 are provided here for you for free. You will also love the ad-free experience on Meritnation's Basic Science Solutions. All Basic Science Solutions for class Class 8 Science are prepared by experts and are 100% accurate.
In the case of diffuse reflection, the rays of light are reflected in different directions.
The image will be formed behind the mirror. It will be at a distance of 10 cm from the mirror.
Three images are formed when an object is placed between two mirrors at right angles to each other.
White light is a mixture of seven colours that blend together in certain proportions and it appears colourless.
Example: light from the sun
Dispersion of light is the splitting of white light into its component colours when it undergoes refraction.
Cornea, the lens and the fluids make up the converging lens system of the eye.
A person with myopia will have difficulty in seeing distant objects.
The first stage of nutritional blindness is the difficulty in seeing distant objects clearly.
The image formed by a shiny metal is not as clear as that formed by a mirror because the rays reflected from the surface of the metal get diffused in different directions.
The following are the laws of reflection:
(a) The angle of incidence is equal to the angle of reflection.
(b) The incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.
The following are the properties of the image formed by a plane mirror:
(a) It is a virtual image.
(b) It is an erect (upright) image.
Lateral inversion refers to the lateral change of the image formed when an object is placed in front of a plane mirror. The right and left sides of the object appear to be reversed in the mirror.
This image is formed at the edge where the two mirrors meet. The image is formed by the rays that get reflected twice and so, it is not laterally inverted.
The light entering the eye is controlled by the iris. In dim light, the iris automatically widens the pupil to let in more light whereas in bright light, the iris contracts the pupil to keep out excess light.
The blind spot of the eye is the region where there are no sense receptors. When the image is formed in this region, the information about it cannot be sent to the brain. Hence we cannot see the image formed in this region.
The process by which the focal length of the lens of the eye is changed to ensure the formation of sharp images of objects at different distances is called accommodation. It is achieved by the contraction and relaxation of ciliary muscles, which change the curvature of the lens, thereby changing the focal length.
Braille is a system invented by Louis Braille. This system has 63 dot patterns or characters. Each character stands for a letter, a combination of letters, a word or punctuation. In the Braille coding, dots are arranged in cells of three rows and two columns. These dots are raised slightly, so that it becomes easier to touch them.
Make a ray box by removing the top of a cardboard box and cutting a window on the side. Make a slit on a piece of chart paper and fix it over the window. Light a torch on the slit to get a ray of light.
Draw a line XY on a sheet of paper and stand a mirror upright, with its back surface on the line. Let a ray from the ray source fall on the mirror. The ray will get reflected. Trace the incident and reflected rays and then remove the mirror. Extend the rays to meet XY at O. Draw a perpendicular (normal) to XY at O and measure the angles of incidence and reflection with a protractor. Repeat the experiment by rotating the sheets. We can observe that both the angles are equal.
The structure of human eye:
The shape of the eye is roughly spherical with an average diameter of around 2.3 cm. The outer part of the eye is quite tough and white in colour. This white part of the eye is known as sclera. The transparent, front outer covering of the eye is known as the cornea. Behind the cornea, there is a coloured membrane known as the iris. It regulates the amount of light entering the eye. It is the coloured part of the eye and gives the eye its colour. In the iris, there is a variable-sized, black circular opening known as the pupil. Its size is controlled by the iris. It is black in colour because most of the light entering it is absorbed by the tissues, which are present in the pupil.
A diet that lacks vitamin A leads to a deficiency called night blindness. In the early stages of the disease, the person is unable to see properly at night. This is followed by extreme dryness of the eye, the softening and clouding of the cornea and other problems. If the person does not take appropriate amount of vitamin A, he will eventually suffer from complete blindness. Night blindness can be cured in the initial stages by taking a high dose of vitamin A and food rich in vitamin A.
1. In regular reflections, the reflected rays remain parallel to each other.
2. The kaleidoscope is a device that uses reflection to produce patterns.
3. The coloured, disc-shaped diaphragm in the eye is called the iris.
4. A person suffering from hypermetropia cannot see nearby objects clearly.
5. The leading cause of blindness is cataract.
6. The set of colours formed on splitting of the white light is called the spectrum of white light.
(b) is diffuse reflection
When light reflects from an irregular surface, the reflected rays are parallel to each other.
(b) and (d)
During reflection of light, the angle of incidence is the angle made by the incident ray with the normal at the point of incidence and it is equal to the angle of reflection.
(b) the number of images decreases as the angle between the mirrors is increased
In multiple reflections from two plane mirrors, the number of images decreases as the angle between the mirrors is increased.
(b) controls the amount of light entering the eye
Iris is the part of eye that controls the amount of light entering the eye.
1. Dispersion of light A. Reflection m. Is formed on the retina
B, o B. Refraction n. Is laterally inverted
2. Image formed on the eye o. Light is split into its component colours
A, m p. Is of the same size as the object
3. Image formed by the plane mirror q. Is very small
A, p r. Is upside down