9TH GRADE PRACTICE
Physics Problems: Light phenomena, Grade 9
Geometric and wave optics, lenses, color and spectra.
Here the conditions and analysis of the solution can be read without an account. In the simulator, you need to collect the same analyzes yourself: “Given,” formulas, order of steps and answer.
Problem statements
The answer options are there to check against, and the walkthrough opens under each problem.
Problem #40
Light propagation and reflectionEvaluate the statement: The incident ray, reflected ray and normal lie in the same plane, and the angles of incidence and reflection are equal.
Show the walkthroughHide the walkthrough
— ?
Angles are measured from the normal to the surface, and not from the surface itself.
Answer
Problem #41
Light propagation and reflectionEvaluate the statement: The concept “Image in a plane mirror” means: In a homogeneous transparent medium, light propagates in a straight line, which allows us to use the ray model.
Show the walkthroughHide the walkthrough
— ?
The construction is carried out by continuation of the reflected rays, which visually converge behind the mirror.
Answer
Problem #42
Reflection of lightThe beam hits the mirror at an angle of 35° to the normal. What is the angle of reflection?
Show the walkthroughHide the walkthrough
— ?
Answer
Problem #43
Refraction and total internal reflectionEvaluate the statement: The absolute indicator is equal to the ratio of the speed of light in a vacuum to the speed of light in a medium.
Show the walkthroughHide the walkthrough
— ?
A larger number means a lower speed of light in the medium and usually a stronger deviation to the normal.
Answer
Problem #44
Refraction and total internal reflectionEvaluate the statement: the concept of “Refraction of light” means: Light is completely reflected when leaving an optically denser medium at an angle greater than the critical one.
Show the walkthroughHide the walkthrough
— ?
When passing into an optically denser medium, the beam usually deviates towards the normal.
Answer
Problem #45
Refraction of lightLight propagates in a transparent medium at a speed of 2·10⁸ m/s. The speed of light in vacuum is 3·10⁸ m/s. Find the indicator.
Show the walkthroughHide the walkthrough
— ?
Answer
Problem #46
Lenses, eyes and optical instrumentsEvaluate the statement: A converging lens turns a parallel beam into a converging one, and a diverging lens makes it divergent.
Show the walkthroughHide the walkthrough
— ?
The type of lens in the medium is determined by the shape of the surfaces and the relative refractive index.
Answer
Problem #47
Lenses, eyes and optical instrumentsEvaluate the statement: The concept of “Constructing an image with a lens” means: The eye focuses the image on the retina, and instruments control the path of rays to magnify or register.
Show the walkthroughHide the walkthrough
— ?
A converging lens can give a real or virtual image, while a diverging lens usually gives an imaginary reduced one.
Answer
Problem #48
LensesThe focal length of the collecting lens is 0.25 m. Find its optical power.
Show the walkthroughHide the walkthrough
— ?
Answer
Problem #49
Interference, diffraction and spectraEvaluate the statement: Stable intensity redistribution when matched light waves are superimposed.
Show the walkthroughHide the walkthrough
— ?
At some points the waves strengthen each other, at others they weaken each other, forming an alternation of maxima and minima.
Answer
Problem #50
Interference, diffraction and spectraEvaluate the statement: The term “Diffraction” means: Dispersion occurs due to the dependence of the refractive index on wavelength and separates white light into colors.
Show the walkthroughHide the walkthrough
— ?
A diffraction grating separates light into wavelengths and is used to observe spectra.
Answer
Problem #51
SpectrumThe wavelength of light in a vacuum is 600 nm. Find the frequency at c = 3·10⁸ m/s.
Show the walkthroughHide the walkthrough
- =
— ?
Answer
The theory behind these problems
Work through the topic if a problem will not give in.
Formulas by topic
Look up symbols and units of measurement in the reference.