If gravitational force is strong enough, light itself is affected by the gravity. The gravitational force of a black hole is so intense that light cannot escape from it. No light, nothing to see. It appears as a "black hole".
It was to dark to to see
There are no black holes but there are dark areas known as Sun spots.
Black holes are not made up of dark matter. Dark matter is a mysterious substance that makes up a large portion of the universe's mass, but black holes are formed from the collapse of massive stars.
Dark matter and black holes are both mysterious components of the universe, but they are not directly related. Dark matter is an invisible substance that makes up a large portion of the universe's mass, while black holes are extremely dense regions in space where gravity is so strong that not even light can escape. While dark matter may influence the formation and behavior of black holes, they are fundamentally different phenomena in the cosmos.
Yes and no. It is rather hard to explain, because black holes are so dark and black that no living creature can see them, which in a sense makes them invisible, but you can also see where a black hole is because it sucks in light, too, so that would also, in a sense make it visible, but the my main answer would be, no black holes are not invisible.
The Dark Side
No. Black holes are huge stars that have collapsed so far that their force of gravity is so enormous that even light cannot escaple. (Hence, they are 'dark' )
No. Black holes do not give off anything other than small amounts of Hawking radiation. That note aside, scientists do not know what dark matter is or what its origin is.
No. The apparent dark areas on the sun are not black holes; they are sunspots. Sunspots are areas of the sun's surface that are not as hot as their surroundings.
No. And the term is "black hole," not "dark hole."
I think that's unlikely. The only relevant features of black holes are its mass, electric charge, and rotational momentum. What makes dark matter different to baryonic ("normal") matter is that it doesn't interact with normal matter, except through gravity - so it seems that none of the differences would be relevant, once such matter is converted to a black hole.
Due to light being unable to escape the black hole, we cann't see it! It's like trying to see in a dark room with a flashlight, that has dead batteries. You cann't see the light because their is none to reflect.