Question

let's find out all the adverbs and the related verbs from the lesson the prince of panidihing and make a list as follows​

Answer 1

Answer:

Reference Standard

After defining a unit of measurement such

as the kilogram or the metre, scientists

agreed on reference standards that make

it possible to calibrate all measuring

devices. For getting reliable measurements,

all devices such as metre sticks and

analytical balances have been calibrated by

their manufacturers to give correct

readings. However, each of these devices

is standardised or calibrated against some

reference. The mass standard is the

kilogram since 1889. It has been defined

as the mass of platinum-iridium (Pt-Ir)

cylinder that is stored in an airtight jar at

International Bureau of Weights and

Measures in Sevres, France. Pt-Ir was

chosen for this standard because it is

highly resistant to chemical attack and its

mass will not change for an extremely long

time.

Scientists are in search of a new

standard for mass. This is being attempted

through accurate determination of

Avogadro constant. Work on this new

standard focuses on ways to measure

accurately the number of atoms in a welldefined mass of sample. One such method,

which uses X-rays to determine the atomic

density of a crystal of ultrapure silicon, has

an accuracy of about 1 part in 106 but has

not yet been adopted to serve as a

standard. There are other methods but

none of them are presently adequate to

replace the Pt-Ir cylinder. No doubt,

changes are expected within this decade.

The metre was originally defined as the

length between two marks on a Pt-Ir bar

kept at a temperature of 0°C (273.15 K). In

1960 the length of the metre was defined

as 1.65076373 × 106 times the wavelength

of light emitted by a krypton laser.

Although this was a cumbersome number,

it preserved the length of the metre at its

agreed value. The metre was redefined in

1983 by CGPM as the length of path

travelled by light in vacuum during a time

interval of 1/299 792 458 of a second.

Similar to the length and the mass, there

are reference standards for other physical

quantities.

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