Spectacles are made up of lenses and are used to improve vision. For nearsightedness, concave lenses are used and for farsightedness convex lenses are used to give clear images. A microscope is an instrument which gives enlarged view of small objects. In an optical microscope, the objective makes a real image of the object which is further magnified by the eyepiece for the eye to see a magnified virtual image. The distance at which the magnified virtual image is formed can be adjusted by moving the eyepiece to suit the power of the spectacles one uses. So, one need not use spectacles while using a microscope in order to see the magnified image clearly. Besides, wearing spectacles also draws the eye of the observer away from the eyepiece thus reducing the field of view.
The pitch, loudness, duration and timbre are the four qualities which define the structure of a piece of music. The pitch or the high-low aspect of the sound is considered to be the most important unit in structuring music. The timbre or the ‘tone colour’ is the sum total of the simultaneous motions produced by any vibrating medium. This is unique for each instrument. The timbre also defines the fineness of the sound produced by an instrument. Differences in timbre of sound produced by different instruments are responsible for the different musical qualities of the various instruments. Thus musical notes produced by different instruments sound different inspite of the pitch being the same.
When we try to break a stick by bending it we use lever of the first kind in which the fulcrum lies between the load points, in this case, right below the point where the stick breaks. Since the force generated at the break point depends on the length of the lever arm, which in this case is the distance from the break point to the stick end, a longer stick is easier to break as it needs less effort compared to that needed to break a short stick.
Natural rubber is made up of long chains of the molecule isoprene with a few cross links between the chains. These kinked, looping polymers are intertwined in un-stretched rubber. When these polymers are subjected to a stretching force, the tangled polymer opens up because of the flexible bonds between the molecules and becomes elongated. When the applied force is released, the chemical bonds in the chains try to come back to their original state. This accounts for rubber’s elasticity.
When an electrical switch is operated it produces a spark at the contact point. This spark emits electromagnetic radiation. Since radio and TV signals are also electromagnetic in nature, the bursts of electromagnetic radiation produced by a spark is also received by the radio or TV set. This produces the disturbance which is heard as crackling sounds on the radio and snowy lines on the TV picture.
One of the laws of fusion is that the melting point of substances which expand on freezing is lowered by the increase of pressure, while it is raised in the case of those which contract on solidification. Ice belongs to the first category of substances, that is, it expands on freezing. Ice has an open structure which collapses when subjected to pressure, producing water which occupies lesser volume. That is why ice melts when subjected to pressure.[custom_search_and_filter]