The electrons in a beam are moving at 18 m/s. (melectron = 9.11 × 10-31 kg, h = 6

626 × 10-34 J ? s)
(a) What is its de Broglie wavelength these electrons?
(b) If the electron beam falls normally on a diffraction grating, what would have to be the spacing between slits in the grating to give a first-order maximum at an angle of 30° with the normal to the grating?


(a) 40 μm (b) 81 μm

Physics & Space Science

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The x component of the velocity of an object vibrating along the x-axis obeys the equation vx(t) = (0.445 m/s) sin[(25.4 rad/s)t + 0.223]

(a) What is the amplitude of the motion of this object? (b) What is the maximum acceleration of the vibrating object?

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The half-life of a radioactive material is 4.5 days. How many days are required for a sample, with an initial activity of 1.0 × 105 Bq, to decay to an activity of 100 Bq?

A) 45 days B) 36 days C) 54 days D) 31 days

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Poor clusters of galaxies often contain an excess of E and S0 galaxies

a. True b. False Indicate whether the statement is true or false

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The three laws dealing with the creation of various spectra are due to:

A) Newton. B) Fraunhofer. C) Kirchhoff. D) Bohr. E) Einstein.

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