Whether the flashlight is a concave mirror or a convex lens

There are two types of flashlights, one with a concave mirror.

One is a convex lens.

Others use both.

Most of the old-fashioned yellowing lights are concave mirrors, and the characteristic is that the glass is flat when viewed from the front.

Nowadays, most of the more expensive LED flashlights are convex lenses, and the characteristic is that the glass is a magnifying glass from the front.

uneven, and many are able to rotate the flashlight head to focus.

Of course, there are some that are used in both, and there are few of them.

Seeing the question you posted, this is obviously only about this question. The question is a light bulb inside a flashlight, not a flashlight.

The concave mirror must be placed behind the bulb, only the convex lens can be made together with the bulb.

There is also a basis for judgment, the concave mirror is a reflector, which can only be placed in the back, and the convex lens is a lens, which can only be placed in the front.

From this, it can be seen that the one in the title is a convex lens.

Concave mirrors, because concave mirrors are good for concentrating light, and the reflected light is parallel rays, which is good for irradiation. And it is a parabola, the light bulb is located at the focal point of the parabola, and the light emitted by the light bulb is closer to the parallel ray through the reflection of the parabola, so that the light of the flashlight shines farther. Let's talk about concave mirrors:

Concave mirrors are reflection imaging. The convex lens is refractive imaging, and the plane mirror is linear imaging, and the resulting image can be: upright, virtual, reduced, and opposite.

Acting as a concentrating light, the mask (including the convex mirror) is not an instrument that transmits light, but reflects it back to imaging, and the light obeys the law of reflection. The concave mirror not only allows the parallel rays to converge in the focal point, but also reflects the light from the focal point into a directional light.

It should be a concave mirror, because the concave mirror is good for concentrating light, and the reflected light is a parallel ray, which is good for irradiation.

I feel like it should be a concave mirror because the convex lens will converge! The flashlight is not converging, it is diffusion.

It looks like a flat mirror at right angles.

Both convex and concave lenses are available, and this is the angle from which to look at.

Concave mirrors. That is, the concave parabolic mirror, which plays the role of concentrating light. Through computer modeling, the luminous angle of the reflector light source and the spatial structure of the LED reflector were simulated, and the refractive trajectory of the light was traced and the curvature of the reflector was adjusted.

Technical parameters to achieve the best light intensity distribution of the flashlight reflector and the functional requirements of the lamp cup for various beam angles, improve the light efficiency of the LED reflector and reduce astigmatism.

The possibility of glare. The reflective surface of the hood Zen can be plated with orange peel and glossy effects. <

The flashlight reflector is a concave mirror, a concave mirror, that is, a concave parabolic mirror, which plays a concentrating role. Through computer modeling, the luminous angle of the reflector light source and the spatial structure of the LED reflector are simulated, the refraction trajectory of the light is traced, and the curvature technical parameters of the reflector are adjusted to achieve the best light intensity distribution of the flashlight reflector and the functional requirements of the lamp cup for various beam angles, so as to improve the light effect dust of the LED reflector and reduce the possibility of astigmatism and glare. The reflective surface can be coated with orange peel and glossy surface.

It can better evenly and softly light spots, without black holes and yellow circles. The imaging principle is reflection imaging, and the imaging is different according to the distance of the object. Convex.

It's refractive imaging. When the parallel light shines on it, it is concentrated on the focal point in front of the mirror through its reflection, the reflective surface is concave, the focus is in front of the mirror, and when the light source is on the focal point, the light emitted is reflected to form a parallel beam. Also called concave mirror.

or jujube converging mirror.

Flashlight reflectors and lenses are two common focusing accessories that can be searched online**. The reflector is the most common and the most common, the formation of the irradiation effect, there is a concentrated beam in the middle, and there is a slightly weaker brightness around the beam, forming a range, focused irradiation mode, which is also the most in line with people's vision habits, because the human eye needs both a concentrated focus and a certain range, so that there will be enough visual width in the night.

Lenses are the opposite, the cheap lenses used in general flashlights are mostly acrylic materials, and generally only have the middle beam, which is slightly better focused than a small-diameter light cup, but not as concentrated as a large-diameter focusing light cup. The irradiation result formed by the lens is generally only one beam, and there is no flood light around, so you will feel that the field of view is a little narrow when you use it, especially at medium and short distances, and the practical value is not as high as that of the light cup flashlight.

I am a titanium lighting for flashlights, and the flashlight with a strong irradiation effect is mainly a C10 flashlight with 800 lumens single-chip Cree XML T6 LED, which has strong flood light at medium and short distances, good long-distance focus, and excellent road illumination effect, which is the first choice for outdoor and night riding. There is also a 18650 small straight with T6 LED, which is small in size and super bright, so you can communicate about it.

a. The concave mirror is used as the reflective surface in the flashlight, in order to gather the light, so that the small bulb located on the concave side of the small light bulb on the Jiaotong point of the small filial piety mirror emits light and shoots out in a straight line, so this option is incorrect;

b. The convex mirror is used as the rear mirror outside the car cab, which is the use of the convex mirror to form an upright and shrinking virtual image.

plays the role of expanding the field of view, so this option is incorrect;

c. Submarines.

on the periscope.

It is composed of two plane mirrors parallel to each other, forming an equal large upright virtual image, which will not bring distant objects closer, so this option is incorrect;

d. The sun cooker is a concave front mirror, using the characteristics of converging light, when boiling water with a sun cooker, the pot can be placed at the focal point to make the temperature of the water easy to rise, so the option is correct

Therefore, choose D

The position of the bulb: the concave mirror has a convergence cover spike imitation effect on the light, the small bulb is placed on the focus of the concave mirror, and the light emitted by the bulb can be reflected by the concave mirror and can be emitted as parallel light; In order to make the light shine very intensively to the distance of the object, the bulb should be placed at the focal point of the lens, so that the light passes through the convex lens.

After refraction, it becomes the propagation mode of parallel light: the concave mirror reflects the light, and the convex lens is the refraction of the light.

Therefore, the answer is shown in the following table: Concave mirror Convex lens Position of the bulb At the focal point of the concave mirror At the focal point of the convex lens The propagation mode of light The reflection of light.

Refraction of light Optical path diagram.

Is the light emitted by a concave mirror (if not refracted again) necessarily a parallel ray?

Of course not, according to the principle of reversibility of light. Light emitted by a point light source must be in focus, or on a line perpendicular to the axis of symmetry between the focal point and the concave mirror, and reflected by the concave mirror to be parallel. Light that is not emitted at this position is not parallel when reflected by a concave mirror.

The position of the bulb in the flashlight is roughly on the focal point of the concave mirror, so the light emitted is reflected by the concave mirror and is basically a parallel light.

The concave surface of the flashlight is coated with a reflective substance, so the reflection of light is used to control the trajectory of light, and it is the principle of reversibility of the optical path is used.

Light rays will only be refracted when they are shot from one medium into another, such as from air into water or glass, but the refracted light and the original light source are only shifted a little, and the angle between them is always 180 degrees, so as long as the refracted light is not reflected and changes the optical path, then it is parallel to the original light source.