please check these:
A concave mirror with a focal length of 10.0 cm creates a real image 30.0 cm away on its principal axis. How far from the mirror is the corresponding object?
a. 20cm
b. 15cm
c. 7.5cm
d. 5.0cm
B
A diffraction grating that contains 650 472 lines/m is illuminated by monochromatic light (wavelength=632.8 nm) from a helium-neon laser directed perpendicular to the surface of the grating. At what angles would one observe the first-order and second-order maxima?
theta1=24.30degrees;theta2=55.38degrees
How is a motor's mechanical energy able to perform mechanical work?
a. mechancial energy is converted into electrical energy
b. a current is generated by a rotating loop in a magnetic field
c. electrical energy is converted into a magnetic force
d. a shaft connected to the rotating coil is attached to some external device
D
the rms current in an ac current is 3.6A. find the maximum current.
a. 5.1 A
b. 4.7 A
c. 2.8 A
d. 1.8 A
A
Which of the following statements about electromagnetic radiation is true?
a. it transfers energy to objects in the path of the electromagnetic waves
b. it can be converted to other energy forms
c. it transports the energy of electromagnetic waves
d. all of the above
B
What causes the dark lines in the absorption spectrum of an element to occur?
a. photons are absorbed when electrons jump from a higher-enegy to a lower-energy state
b.photons are emitted when electrons jump from a higher-energy to a lower-energy state
c. photons are absorbed when electrons jump from a lower-energy to a higher-energy state
d. photons are emitted when electrons jump from a lower-energy to a higher-energy state
C
What is the speed of a 50 g rock if its de Broglie wavelength is 3.32*10^-34 m?
(h=6.63*10^-34 J*s)
a. 40 m/s
b. 30 m/s
c. 20 m/s
d. 60 m/s
A
What does the mass number of a nucleus indicate?
a. the number of neutrons present
b. the number of protons present
c. the average atomic mass of the element
d. the number of neutrons and protons present
D
all correct.
To solve the first question about the concave mirror and the real image, you need to use the mirror equation:
1/f = 1/do + 1/di
Where f is the focal length of the mirror, do is the object distance, and di is the image distance. In this case, the focal length (f) is given as 10.0 cm, and the image distance (di) is given as 30.0 cm. We need to find the object distance (do).
Rearranging the equation, we have:
1/do = 1/f - 1/di
Substituting the given values, we get:
1/do = 1/10 - 1/30
1/do = 3/30 - 1/30
1/do = 2/30
1/do = 1/15
To find do, we can take the reciprocal of both sides:
do = 15 cm
So, the corresponding object distance is 15 cm.
For the second question about the diffraction grating, to determine the angles of the first-order and second-order maxima, you can use the formula:
dsinθ = mλ
Where d is the grating spacing, θ is the angle of the diffracted light, m is the order of the maximum, and λ is the wavelength of the light. In this case, the grating spacing (d) is not given, but the number of lines per meter is given as 650,472 lines/m. We can calculate d using the formula:
d = 1/lines per meter
d = 1/650,472 m
Substituting the given values, we get:
d = 1/650,472 m = 1.535 × 10^-6 m
Now, we can calculate the angles. For the first-order maximum (m = 1):
1.535 × 10^-6 m x sinθ1 = 1 x 632.8 nm
sinθ1 = (632.8 nm) / (1.535 × 10^-6 m)
Using the inverse sine function on a calculator, we can calculate θ1:
θ1 ≈ 24.30 degrees
For the second-order maximum (m = 2):
1.535 × 10^-6 m x sinθ2 = 2 x 632.8 nm
sinθ2 = (2 x 632.8 nm) / (1.535 × 10^-6 m)
Using the inverse sine function on a calculator, we can calculate θ2:
θ2 ≈ 55.38 degrees
So, the angles for the first-order and second-order maxima are approximately 24.30 degrees and 55.38 degrees, respectively.
For the third question about a motor's mechanical energy and performing mechanical work, the correct answer is d. A shaft connected to the rotating coil is attached to some external device. This is because a motor converts electrical energy into mechanical energy, which is then used to perform mechanical work on an external device.
For the fourth question about the rms current and finding the maximum current in an AC circuit, the relationship between the rms current (Irms) and the maximum current (Imax) is given by:
Irms = Imax / sqrt(2)
In this case, the rms current (Irms) is given as 3.6 A. To find the maximum current (Imax), we can rearrange the equation as:
Imax = Irms x sqrt(2)
Substituting the given value, we get:
Imax = 3.6 A x sqrt(2)
Using a calculator, we can calculate the value:
Imax ≈ 5.1 A
So, the maximum current is approximately 5.1 A.
For the fifth question about electromagnetic radiation, the correct answer is b. It can be converted to other energy forms. This is because electromagnetic radiation carries energy and can be transformed into other energy forms, such as thermal energy, electrical energy, or chemical energy.
For the sixth question about the dark lines in the absorption spectrum of an element, the correct answer is c. Photons are absorbed when electrons jump from a lower-energy to a higher-energy state. These dark lines occur because photons of specific wavelengths are absorbed by electrons as they transition from lower-energy to higher-energy states within the atom or molecule, resulting in the absence of those wavelengths in the emitted spectrum.
For the seventh question about the speed of a rock and its de Broglie wavelength, you can use the de Broglie wavelength equation:
λ = h / (mv)
Where λ is the de Broglie wavelength, h is the Planck's constant (h = 6.63 × 10^-34 J*s), m is the mass of the object, and v is its velocity. In this case, the mass (m) of the rock is given as 50 g (convert to kg: 0.05 kg), and the de Broglie wavelength (λ) is given as 3.32 × 10^-34 m. We need to find the speed (v) of the rock.
Rearranging the equation, we have:
v = h / (mλ)
Substituting the given values, we get:
v = (6.63 × 10^-34 J*s) / (0.05 kg × 3.32 × 10^-34 m)
v = 40 m/s
So, the speed of the rock is 40 m/s.
For the last question about the mass number of a nucleus, the correct answer is d. The mass number indicates the number of neutrons and protons present in the nucleus. The mass number represents the total number of nucleons (protons and neutrons) in an atomic nucleus.