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Mixtures of red chilli powder in water, butter in water, petrol in water, and honey in water were given to Radha, Sudha, Sofia and Raveena, respectively. Whose mixture is in solution form?

Answer: Raveena will get the mixture in solution form. Since honey and water are soluble with each other hence a solution will be formed when... View Article

lt was Paheli’s birthday. Her grandmother gave her two gifts made of metals, one old dull silver spoon and a pair of lustrous gold earrings. She was surprised to see the difference in the appearance of the two metals. Can you explain the reason for this difference?

Answer: Because it was old and had been exposed to air for a long time, the silver spoon appeared dull. When silver is exposed to air, it reacts... View Article

Which type of the following materials is used for making the front glass (windscreen) of a car? (a) Transparent (b) Translucent (c) Opaque (d) All the above

Answer: (a) Transparent Transparent glass is used for making the front glass of a car so that everything can be seen clearly. Transparent... View Article

Find the odd one out from the following. (a) Tawa (b) Spade (c) Pressure cooker (d) Eraser

Answer: (d) Eraser Eraser is made up of rubber while Tawa, Pressure cooker and spade are made up of metal. Metals are minerals or substances... View Article

Which of the following statements is not true? (a) Materials are grouped for convenience. (b) Materials are grouped to study their properties. (c) Materials are grouped for fun. (d) Materials are grouped according to their uses.

Answer: (c) Materials are grouped for fun. Materials aren't grouped for the sake of fun. There's a reason they're grouped together. Materials are... View Article

Which of the following materials is not lustrous?(a) Gold (b) Silver (c) Wood (d) Diamond

Answer: (c) Wood Lustrous is defined as metals that have a shiny appearance. The shiny appearance of the metals is called metallic lustre. Wood... View Article

Which among the following are commonly used for making a safety pin? (a) Wood and glass (b) Plastic and glass (c) Leather and plastic (d) Steel and plastic

Answer: (d) Steel and plastic Steel can be moulded to get sharp points and plastic is used to seal the edges. Hence steel and plastic are used... View Article

Which pair of substances among the following would float in a tumbler half-filled with water? (a) Cotton thread, thermocol (b) Feather, plastic ball (c) Pin, oil drops (d) Rubber band, coin

Answer: (b) Feather, plastic ball Feather and plastic balls will float on the water since they are lighter than water. An object sinks in water... View Article

While doing an activity in class, the teacher asked Paheli to handover a translucent material. Which among the following materials will Paheli pick and give her teacher? (a) Glass tumbler (b) Mirror (c) Muslin cloth (d) Aluminium foil

Answer: (c) Muslin cloth Transparent substances are those substances or materials that allow things to be seen through them. Almost all light... View Article

Boojho found a bag containing the following materials. (i) Mirror (ii) Paper stained with oil (iii) Magnet (iv) Glass spectacles Help Boojho in finding out the material(s) which is/are opaque.

Answer: (c) (i) and (iii) Transparent substances are those substances or materials that allow things to be seen through them. Almost all light... View Article

You are provided with the following materials (i) magnifying glass (ii) mirror (iii) stainless steel plate (iv) glass tumbler. Which of the above materials will you identify as transparent? (a) (i) and (ii) (b) (i) and (iii) (c) (i) and (iv) (d) (iii) and (iv)

Answer: (c) (i) and (iv) Transparent substances are those substances or materials that allow things to be seen through them. Almost all light... View Article

Pick one material from the following which is completely soluble in water. (a) Chalk powder (b) Tea leaves (c) Glucose (d) Sawdust

Answer: (c) Glucose Completely soluble implies when we pour some compounds into water, they become totally soluble. Their particles are invisible... View Article

An iron nail is kept in each of the following liquids. In which case would it lose its shine and appear dull? (a) Mustard oil (b) Soft drink (c) Coconut oil (d) Kerosene

Answer: (b) Soft drink Because soft drinks contain carbonic acid, which reacts with the iron nail. An iron nail kept in a soft drink will lose... View Article

A student-focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under Position of candle = 12.0 cm Position of convex lens = 50.0 cm Position of the screen = 88.0 cm i) What is the focal length of the convex lens? ii) Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm? iii) What will be the nature of the image formed if he further shifts the candle towards the lens? iv) Draw a ray diagram to show the formation of the image in case (iii) as said above.

Answer: Position of candle = 12.0 cm Position of convex lens = 50.0 cm Position of the screen = 88.0 cm (i) u = Distance of candle from... View Article

Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them?

Answer: Degree of convergence and divergence provided by a lens is called the power of the lens. Unit of power of lens is Diopter D. 1 dioptre... View Article

Size of the image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image and the mirror?

Answer: m = 1/3 Using magnification formula m = -v/u 1/3 = -v/u v = -u/3 From mirror formula 1/v + 1/u = 1/f -u/3 + 1/u = 1/20 u =... View Article

The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between the lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?

Answer: As the image is obtained on the screen, it is real. so, Magnification (m) = –3 v = 80 cm u =? As m = v/u so, –3 = 80/u u =... View Article

Draw ray diagrams showing the image formation by a convex mirror when an object is placed (a) at infinity (b) at a finite distance from the mirror

Answer: If the cut part of the hollow sphere is painted from inside, then its outer surface becomes the reflecting surface. This kind of mirror... View Article

Draw ray diagrams showing the image formation by a concave lens when an object is placed (a) at the focus of the lens (b) between focus and twice the focal length of the lens (c) beyond twice the focal length of the lens

Answer: (a) at the focus of the lens The ray diagram when the object is placed at the focus of the concave lens: (b) between focus and twice... View Article

Write laws of refraction. Explain the same with the help of a ray diagram, when a ray of light passes through a rectangular glass slab.

Answer: The angle of incidence is the angle between the incident ray and the normal, denoted as ‘i’. The angle of refraction is the angle... View Article

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