10^-6m equivalent of 1 \(\mu\) m
1 metre is equivalent to \({{1}\over{{10}^{-6}}}={10}^{6}\mu\) m
In one metre 10⁶ microns are present

9.467\(\times\)10¹⁵m is equivalent to 1 ly.
1 metre is equivalent to \({{1}\over{9.467\times{10}^{15}}}\)
= 0.1056\(\times\)10^-15
= 1.05\(\times\)10^-16 ly
In one metre, 1.05\(\times\)10^-16 light years are present.

1.496\(\times\)10¹¹m is equivalent to 1 AU.
1 metre is equivalent to \({{1}\over{1.496\times{10}^{11}}}\)
= 0.6884\(\times\)10^-11
= 6.68\(\times\)10^-12 AU
In one more, 6.68\(\times\)10^-12 astronomical units are present.

(i) By choosing the instrument carefully.
(ii) Necessary correction is to be made.
(iii) High precision instrument is to be used.
(iv) Proper setting up of experiments is to be done.
(v) Taking proper precautions is a must, while making observations

(i) Biological studies are impossible without a microscope designed using physics principles.
(ii) The invention of the electron microscope has made it possible to see even the structure of a cell. X-ray and neutron diffraction techniques have helped us to understand the structure of nucleic acids, which help to control vital life processes. X-rays are used for diagnostic purposes.
(iii) Radio-isotopes are used in radiotherapy for the cure of cancer and other diseases. In recent years, biological processes are being studied from the physics point of view.

(i) Basic laws of electricity and magnetism led to the discovery of wireless communication technology which has shrunk the world with effective communication over large distances.
(ii) The launching of satellite into space has revolutionized the concept of communication.
(iii) Microelectronics, lasers, computers, superconductivity and nuclear energy have comprehensively changed the thinking and living style of human beings.

(i) Theoretical predictions aided with recent simulation and computation procedures are widely used to identify the most suited materials for robust applications.
(ii) The pharmaceutical industry uses this technique very effectively to design new drugs. Bio compatible materials for organ replacement are predicted using quantum prescriptions of physics before fabrication.
(iii) Thus, experiments and theory work, hand in hand, complementing one another.

(i) Attempting to explain diverse physical phenomena with a few concepts and laws is unification.
(ii) Newton's universal law of gravitation explains the motion of freely falling bodies towards the Earth, motion of planets around the Sun, motion of the Moon around the Earth, thus unifying the fundamental forces of nature.

No. AU and A represent the two different units of length.
1 AU = 1 astronomical unit = 1.496\(\times\)10¹¹m
1 \(\mathring{A}\) = 1 angstrom = 10^-10 m

Gross Error
(i) The error caused due to the shear carelessness of an observer is called gross error.
For example:
(ii) Reading an instrument without setting it properly.
(iii) Taking observations in a wrong manner without bothering about the sources of errors and the precautions.
(iv) Recording wrong observations. These errors can be minimized only when an observer is careful and mentally alert.

(i) This system makes use of only one unit for one physical quantity, which means a rational system of units.
(ii) In this system, all the derived units can be easily obtained from basic and supplementary units, which means it is a coherent system of units.
(iii) It is a metric system which means that multiples and submultiples can be expressed as powers of 10.

(i) 1 Mega ohm (M\(\Omega\)) = 10⁶\(\Omega\)
(ii) 1 milliampere (mA) = 10^-3A
(iii) 1 daca gram (da g) = 10g
(iv) 1 nano second (ns) = 10^-9s
(v) 1 microvolt (\(\mu\)Y) = 10^-6y
(vi) 1 centimetre (cm) = 10^-2m

The SI unit for Luminous intensity is candela. Its symbol is cd.
Definition:
One candela is the luminous intensity in a given direction, of a source that emits monochromatic radiation of frequency 5.4\(\times\) 10⁴ Hz and that has a radiant intensity of \({{1}\over{638}}\) watt/steradian in that direction.

Fundamental units:
The units in which the fundamental quantities are measured are called fundamental units. It is also known as base units.
Derived units:
The units of measurements of all other physical quantities, which can be obtained by a suitable multiplication or division of powers of fundamental units are called derived units.
Example:
Unit of speed = \({{Unit\ of\ distance}\over{Unit\ of\ \ time}}\)
\(={{m}\over{s}}={ms}^{-1}\)
ms^-1 is a derived unit.

(i) Basic laws of electricity and magnetism led to the discovery of wireless communication technology which has shrunk the world with effective communication over large distances.
(ii) The launching of satellite into space has revolutionized the concept of communication.
(iii) Microelectronics, lasers, computers, superconductivity and nuclear energy have comprehensively changed the thinking and living style of human beings.