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Science [ 2 Marks Questions ]

T3 CH1 Light · Tamil Nadu Board STD 7 (Tamil - English Medium). 28 questions.

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[ 2 Marks Questions ]

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28 questions · timed · auto-graded

Question 12 Marks
Explain with examples, why some capital letters look the same in a mirror but others are reversed.
Answer
Any letter that has a bilateral symmetry will have its mirror image the same as that of the object.
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Question 22 Marks
Describe the pictures.
>
>Image
Answer
  1. When the tube is bent, we cannot see the source of light
  2. When the tube is held straight we can see the flame. The two pictures verify that light travels in straight lines. This is known as rectilinear propagation of light.
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Question 32 Marks
Write about two everyday situations that tell you that light travels in a straight line.
Answer
  1. Formation of shadow: Shadows are formed when some light rays continue its travel in straight lines while other rays are stopped by an object.
  2. When there is a small hole in a room, light travels only in a straight line.
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Question 42 Marks
What is a shadow? What things are necessary for the formation of a shadow?
Answer
  1. Shadows are formed because light travels in straight lines.
  2. Shadow is always against, opposite side of light source.
  3. Shadow is formed by opaque objects that stop high from propagating.
  4. Things necessary for the formation of shadow: source of light, opaque object
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Question 52 Marks
Rajan was playing with the mirror images of a clock. He looked at the clock in his room. It was showing 1:40. Draw the position of the hands on the real clock and on its mirror reflection. Write below the picture what time each picture is showing.

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Question 62 Marks
Two plane mirrors M1 and M2 are placed perpendicular with each other, as shown in figure. The ray AB makes an angle 39 ° with the plane mirror M1, then

  1. The reflected rays are ______ ______
  2. The incident rays are ______ ______
  3. What is the angle of incident corresponding to the ray BC?
  4. What is the angle of reflection corresponding to the ray CD
Answer
  1. BC, CD
  2. AB, BC
  3. i = 39°
  4. r = 39°
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Question 72 Marks
Why is the writing on the front of an ambulance back to front as shown in the picture?

Answer
  1. This is due to lateral inversion.
  2. The phenomenon due to which the left side of an object appears to be right side of the object in its image in a reflecting medium (mirror).
  3. So that drivers see the word the right way around in their rear-view mirror.
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Question 92 Marks
A boy of height 1m 45 cm is standing in front of a long mirror at a distance of 2 m. From this information, fill up the following sentences:
  1. The distance between the boy and his image is ______
  2. The height of the image is______
  3. When the boy moves 1m forward, the distance between her and her image is______
Answer
  1. The distance between the boy and his image is 4m.
  2. The height of the image is same.
  3. When the boy moves 1m forward, the distance between her and her image is 2m
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Question 102 Marks
What do you mean by visible light?
Answer
Visible light is a spectrum of a number of waves with different wavelength range from 400nm to 700nm (lnm = 10″9 meter) each wave has a definite wavelength represents a particular colour.
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Question 112 Marks
A person is looking at the image of a tree in a mirror placed 3.5 m in front of him. Given that the tree is at 0.5 m behind his eyes. Find the distance between the image of the tree and his eyes. What are needed to see an object?
Answer

Distance between the person and the mirror = 3.5 m
Distance between the person and tree (object) = 0.5 m
The image formed in the mirror = 4 m
The distance between the image of the tree and his eyes = 4 + 3.5 = 7.5
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Question 122 Marks
Figure shows a pencil placed above a mirror

A.Draw its image formed by the mirror
B.Show how light rays from the object are reflected at the mirror to form the image for the eye.
Answer


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Question 132 Marks
With the help of a diagram, state the laws of reflection
Answer
Laws of reflection
  1. The angle of incidence is always equal to the angle of reflection li =l*
  2. The incident ray, the reflected ray and the normal at the point of incidence lie on the same plane.
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Question 142 Marks
Ram planned an activity to observe an object through pipes as shown in figure, so that he could see objects which he could not directly see.
Image
(a) Mention how many mirrors should he use to see the objects.
(b) If any of the mirrors is removed, will he be able to see the objects?
(c) Indicate the positions of the mirrors in the figure.
Answer
(a) Number of mirrors = 3
(b) He will not be able to see the objects if any of the mirror is removed, since he will not get the rays after removal of mirror.
Image
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Question 152 Marks
Imagine that parallel rays are incident on an irregular surface. Are the rays reflected from this surface parallel to each other?
Answer
No, the reflected rays from irregular surface are in different directions.
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Question 162 Marks
Why are we able to see the tap water in a glass even though it is colourless?
Answer
Top water reflects the light into our eyes. As long as an object reflects light into our eyes, we can see it.
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Question 172 Marks
A plane mirror forms a virtual image. The distance between Maria and her image in a plane mirror is 10 m. How much distance should she move in order to get the distance of 5 m between herself and her image?
Answer
Image
The distance between Maria and her image in a plane mirror = 10 m
Image
So, she shouuld move a distance of 2.5 m toward the plane mirror
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Question 182 Marks
A ray of light fall on a plane surface at an angle of incidence 9° and reflection occurs. Calculate the angle of reflection in degree.
Answer
By first law of reflection, angle of incidence is always equal to angle of reflection. $\left\lfloor i=\left\lfloor r\right.\right.$. Here, angle of incidence is $9^{\circ}$. So angle of reflection must be equal to $9^{\circ}$.
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Question 192 Marks
Calculate the number of images formed by plane mirrors kept at an angle of 10° to each others.
Answer
Number of image $n=\frac{360^{\circ}}{\theta}-1=\frac{360^{\circ}}{10^{\circ}}-1$
$=36-1$
$=35$ images
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Question 202 Marks
When lighting a bulbs in a dark room, light spreads the whole room quickly. Give reason.
Answer
  1. When lighting a bulb in a dark room, light spreads the whole room quickly.
  2. This is because the light travels very fast.
  3. Light travels three lakh kilometers per second in air or vacuum.
  4. In theory, nothing can travel faster than light.
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Question 212 Marks
What is meant by synthesis of colour?
Answer
  1. Synthesis of colour is the method of creating colour by mixing various proportion of two (or) three distinct colours of light. .
  2. These distinct colours are Red, Green and Blue called as primary colours.
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Question 222 Marks
Why danger lights in vehicles are red in colour?
Answer
  1. Red color is scattered the least by air molecules.
  2. Red color has the highest wavelength of all the other colors. So red color is able to travel the longest distance through air, fog.
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Question 232 Marks
What is lunar eclipse?
Answer
  1. Lunar eclipse occurs, when the Earth (E) comes between the Sun (S) and the Moon (M).
  2. The Earth prevents light coming from the Sun and makes shadow on the Moon. This is lunar eclipse.
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Question 242 Marks
Define opaque material. Give example.
Answer
  1. Materials that are not able to allow light to pass through, are called opaque material.
  2. Example: Wall, thick card board, stone, etc.
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Question 252 Marks
Define transparent materials. Give example.
Answer
  1. Materials that allow light to pass through completely are known as transparent material.
  2. Example: Eye glasses, clear drinking glass, clear water, face glasses used in buses.
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Question 262 Marks
State laws of reflection.
Answer
Laws of reflection:
  1. The angle of incidence is always equal to the angle of reflection. ⌊i = ⌊r
  2. The incident ray, the reflected ray and the normal at the point of incidence lie on the same plane.
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Question 272 Marks
Mention the properties of light.
Answer
Light has some fundamental properties as mentioned below.
  • Rectilinear propagation of light
  • Reflection
  • Speed
  • Interaction of light with matter.
  1. Types of material according to permeability.
  2. Formation of shadows.
  3. Plane mirror and images.
  4. Spectrum.
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Question 282 Marks
What is natural sources of light? Give example.
Answer
Sources which emit light naturally are known as natural sources of light. The Sun is the primary and the major source of natural light.
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[ 2 Marks Questions ] - Science STD 7 Questions - Vidyadip