Mix Examples - Sources of Energy Questions in English

(FALSE) The statement is False.
Explanation: Glass is transparent to visible light and infrared radiation (heat),but it is opaque to ultraviolet $(UV)$ radiation. The glass cover of a solar cooker allows short-wavelength visible light to enter,which is then absorbed by the black interior and converted into heat (infrared radiation). This heat is trapped inside because glass does not allow long-wavelength infrared radiation to escape easily (the greenhouse effect). It does not allow $UV$ radiation to pass through.

(A) The statement is True.
Solar heating devices,such as solar cookers,often use concave (spherical) reflectors to focus parallel rays of sunlight onto a single point (the focus).
By concentrating the solar energy onto a small area,the intensity of heat increases significantly,allowing for the attainment of high temperatures required for cooking or heating purposes.

(TRUE) True.
Solar cells,also known as photovoltaic cells,are devices that convert light energy directly into electricity using the photovoltaic effect. These cells are primarily constructed from semiconductor materials,most commonly silicon,which possess the unique property of generating an electric current when exposed to light.

(B) The statement is False.
Modern commercial silicon-based solar cells typically have an efficiency ranging from $15 \%$ to $20 \%$.
Selenium solar cells,which were among the earliest types developed,have a much lower efficiency,typically less than $1 \%$.
Therefore,the claim that a selenium solar cell can convert $25 \%$ of sunlight into electrical energy is incorrect.

(FALSE) The statement is False.
Solar cells and solar panels are highly effective in remote areas where conventional electricity grids are difficult or expensive to install. They provide a reliable and sustainable source of energy for lighting,water pumping,and communication in off-grid locations.