• By the term ‘mirror’ we mean a shiny piece of glass, that is polished from the back, which reflects a clear image of the object, placed in front of it. On the other hand, Lens is a transparent piece of glass, with a spherical surface, that concentrates or disperses the rays of light falling on it.
• A mirror is either plane or spherical. In contrast, a lens has two surfaces, at least one of which is curved inwards or outwards.
• As the light ray strikes the mirror, it reflects off the light in a different direction, resulting in the formation of an image. Conversely, in case of lenses, the light ray enters the medium (lens), which refracts (bends) the rays in a different direction, creating a focus, from where the rays seem to originate.

 A concave lens can only form virtual, erect and diminished image of an object. As virtual and erect image formed by a convex lens is always magnified.

(1) Safety services towards cyclone and other disaster by Government and other agencies:

• Cyclone forecast and warning services: With the advances in technology, cyclone can be forecast in about 24 to 48 hours in advance. This becomes possible because of satellites and computers. When a cyclone is nearer to the coastline, the cyclone warning is forecasted almost at every half an hour.
• Rapid communication to the Government and concerned people: Communication about the cyclone is given quickly to the Government and the people so that proper safety measures and rescue operations can be carried out.
• Construction of cyclone shelters in the cyclone prone area.
• Shifting the people quickly to a safer place.

(2) Action on the part of people:

• Pay attention towards warning broadcasts from time to time.
• In case of a cyclone warning, stock necessary food items and medicines.
• If possible, move to a safer place.
• Fishermen should not venture into the sea during a cyclone warning.
• Cooperate with others in the community.
• Help the rescue team.

A forest is an ecosystem where there is a cross-linked interaction among species through food webs and genetics. That is why nothing goes waste.
Example: Plants absorb solar energy and rainwater from ground and produces food. This food is eaten by primary, then secondary and tertiary consumers. When they die, they are decomposed by bacteria in soil which makes it fertile. When plants die, they too are decomposed by bacteria in soil and the seeds produced by them fall in the soil giving rise to another plant. In the same way, the offspring of parent animals grow and this entire process is repeated again and again. Therefore, nothing goes waste in a forest.

Ingestion: The intake of food is called ingestion. Method of ingestion, i.e. taking of food, varies from one animal to another.
Causes of Indigestion
General causes of indigestion are stated below:

• Smoking.
• Musty foods.
• Excess of alcohol.
• Intake of large quantities of beverages.
• Too much of mental stress, depression.
• Performing more physical task soon after the meal.

Process of food making in green plants:
Green plants make their food themselves. Green leaves make food from Carbon dioxide and water in the presence of sunlight and chlorophyll.

Leaves have several tiny pore-like structures on the lower surface. Such a pore is called stomata through which leaves absorb carbon dioxide from air. Water is transported to the leaves through hair like pipelines from the roots. These pipelines are present throughout the plant, i.e. from roots to branches and leaves. These pipe-lines are known as Xylem. Xylem is a type of tissue. Chlorophyll, a green pigment, is found in green leaves. Chlorophyll absorbs sunlight and gives energy. Chloroplast is the site of photosynthesis. Carbohydrate is used as food and oxygen is emitted out to atmosphere. This whole process of making food by plants is called photosynthesis.

The uptake of nutrients by organism from dead and decaying matter in the form of solution is called the saprotrophic nutrition. The organisms which use saprotrophic mode of nutrition are called saprotrophs.  Saprotrophs secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients from it. For example: fungi, Rhizopus, asperigillus, mushrooms.

Uses of Concave Lenses

• Concave lenses are used for correcting myopia or short-sightedness.
• Concave lenses are used on flashlights to magnify the light produced by the bulb.
• Used in peepholes of house doors for security to provide a view of people or objects outside the doors.

Water is available in all the three states of matter. Ice is the solid state, water is the liquid state and vapour is the gaseous state; in which water is available. The water on the earth keeps on changing in all the three states in a cycle. This is known as water cycle. The water cycle helps in keeping the amount of water on the earth as constant.
Following are the main steps of water cycle in nature:
Evaporation: Water from the surface of the earth keeps on evaporating and turns into vapour. The water vapour also comes from green plants through transpiration.
Condensation: The water vapour condenses to from clouds.
Precipitation: Water from the clouds falls on the land; in the form of precipitation. At higher altitudes, the condensed water from the clouds also falls in the form of ice.
Collection: The rainwater falls on the ground and runs off to the nearest water bodies. Some of this water seeps down the ground to recharge the groundwater. Rest of the water goes to the ocean via rivers.

Cloth is one of our basic needs. Cloth protects us from heat, cold, rain, dust, insects, etc. Clothes also make one civilized and smart. Clothes are made of cloth. Cloth is also known as fabric. Fabric is made of fiber.
Types of Fibre
There are two types of fibre, viz. natural and man-made.
Natural fibers: Natural fibers are obtained from plants and animals; such as jute, cotton, wool, silk, etc.
Man-made fibers: Fibers that are synthesized in laboratory are called man-made fiber, such as terrylene, terry-cotton, acrylic, etc.